Fix spotbugs errors

[DomGarguilo]

This PR fixes all spotbugs errors currently present.

Before these changes the following errors were present:

errors

``` [ERROR] Medium: Dead store to simpleTimerThreadpoolSize in org.apache.accumulo.proxy.Proxy.createProxyServer(HostAndPort, TProtocolFactory, Properties) [org.apache.accumulo.proxy.Proxy] At Proxy.java:[line 190] DLS_DEAD_LOCAL_STORE [ERROR] Medium: Write to static field org.apache.accumulo.proxy.its.SimpleProxyBase.client from instance method org.apache.accumulo.proxy.its.SimpleProxyBase.namespacePermissions() [org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase] At SimpleProxyBase.java:[line 1677]Another occurrence at SimpleProxyBase.java:[line 1694]Another occurrence at SimpleProxyBase.java:[line 1709]Another occurrence at SimpleProxyBase.java:[line 1715]Another occurrence at SimpleProxyBase.java:[line 1728]Another occurrence at SimpleProxyBase.java:[line 1736]Another occurrence at SimpleProxyBase.java:[line 1748] ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD [ERROR] Medium: Write to static field org.apache.accumulo.proxy.its.SimpleProxyBase.client from instance method org.apache.accumulo.proxy.its.SimpleProxyBase.setup(TestInfo) [org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase] At SimpleProxyBase.java:[line 294]Another occurrence at SimpleProxyBase.java:[line 322] ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD [ERROR] Medium: Write to static field org.apache.accumulo.proxy.its.SimpleProxyBase.creds from instance method org.apache.accumulo.proxy.its.SimpleProxyBase.setup(TestInfo) [org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase] At SimpleProxyBase.java:[line 295]Another occurrence at SimpleProxyBase.java:[line 323] ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD [ERROR] Medium: Write to static field org.apache.accumulo.proxy.its.SimpleProxyBase.client from instance method org.apache.accumulo.proxy.its.SimpleProxyBase.testConditionalWriter() [org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase] At SimpleProxyBase.java:[line 2510]Another occurrence at SimpleProxyBase.java:[line 2541]Another occurrence at SimpleProxyBase.java:[line 2553]Another occurrence at SimpleProxyBase.java:[line 2572]Another occurrence at SimpleProxyBase.java:[line 2585]Another occurrence at SimpleProxyBase.java:[line 2602]Another occurrence at SimpleProxyBase.java:[line 2614]Another occurrence at SimpleProxyBase.java:[line 2629] ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD [ERROR] Medium: Write to static field org.apache.accumulo.proxy.its.SimpleProxyBase.client from instance method org.apache.accumulo.proxy.its.SimpleProxyBase.userPermissions() [org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase, org.apache.accumulo.proxy.its.SimpleProxyBase] At SimpleProxyBase.java:[line 1516]Another occurrence at SimpleProxyBase.java:[line 1533]Another occurrence at SimpleProxyBase.java:[line 1545]Another occurrence at SimpleProxyBase.java:[line 1551]Another occurrence at SimpleProxyBase.java:[line 1562]Another occurrence at SimpleProxyBase.java:[line 1570]Another occurrence at SimpleProxyBase.java:[line 1579]Another occurrence at SimpleProxyBase.java:[line 1591]Another occurrence at SimpleProxyBase.java:[line 1603]Another occurrence at SimpleProxyBase.java:[line 1615]Another occurrence at SimpleProxyBase.java:[line 1625]Another occurrence at SimpleProxyBase.java:[line 1637]Another occurrence at SimpleProxyBase.java:[line 1648] ST_WRITE_TO_STATIC_FROM_INSTANCE_METHOD [ERROR] Medium: org.apache.accumulo.proxy.its.TestProxyClient.proxy() may expose internal representation by returning TestProxyClient.proxy [org.apache.accumulo.proxy.its.TestProxyClient] At TestProxyClient.java:[line 95] EI_EXPOSE_REP ```

The main change that needs review is the change in TestProxyClient.java. These changes return a new AccumuloProxy.Client object for each call to proxy(). This was done to avoid the following error:

[ERROR] Medium: org.apache.accumulo.proxy.its.TestProxyClient.proxy() may expose internal representation by returning TestProxyClient.proxy [org.apache.accumulo.proxy.its.TestProxyClient] At TestProxyClient.java:[line 95]

This change seems fine to me but I wouldn't be surprised if there is something I am overlooking that would make it so that this is not something we want to do. This is the only way I could find to fix this error.