Use Java11 for container.

[cmvelo]

It appears that using Java 17 (which is what the docker container defaults to) breaks some of the tests with the following error:

<failure message="java.lang.NoClassDefFoundError: Could not initialize class io.netty.util.internal.PlatformDependent0" type="java.lang.NoClassDefFoundError">java.lang.NoClassDefFoundError: Could not initialize class io.netty.util.internal.PlatformDependent0
        at io.netty.util.internal.PlatformDependent.&lt;clinit&gt;(PlatformDependent.java:101)
        at io.netty.util.ConstantPool.&lt;init&gt;(ConstantPool.java:32)
        at io.netty.util.Signal$1.&lt;init&gt;(Signal.java:27)
        at io.netty.util.Signal.&lt;clinit&gt;(Signal.java:27)
        at io.netty.util.concurrent.DefaultPromise.&lt;clinit&gt;(DefaultPromise.java:42)
        at io.netty.util.concurrent.GlobalEventExecutor.&lt;init&gt;(GlobalEventExecutor.java:44)
        at io.netty.util.concurrent.GlobalEventExecutor.&lt;clinit&gt;(GlobalEventExecutor.java:41)
        at com.datastax.driver.core.Connection$Factory.&lt;init&gt;(Connection.java:969)
        at com.datastax.driver.core.Cluster$Manager.init(Cluster.java:1665)
        at com.datastax.driver.core.Cluster.init(Cluster.java:214)
        at com.datastax.driver.core.Cluster.connectAsync(Cluster.java:387)
        at com.datastax.driver.core.Cluster.connectAsync(Cluster.java:366)
        at com.datastax.driver.core.Cluster.connect(Cluster.java:311)
        at smartthings.ratpack.cassandra.CassandraServiceSpec.setupSpec(CassandraServiceSpec.groovy:31)
</failure>

[codecov[bot]]

Codecov Report

Base: 37.57% // Head: 37.57% // No change to project coverage :thumbsup:

Coverage data is based on head (0fcefee) compared to base (ca74c58). Patch has no changes to coverable lines.

:exclamation: Current head 0fcefee differs from pull request most recent head 8b0fb70. Consider uploading reports for the commit 8b0fb70 to get more accurate results

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #37 +/- ## ========================================= Coverage 37.57% 37.57% Complexity 8 8 ========================================= Files 6 6 Lines 165 165 Branches 10 10 ========================================= Hits 62 62 Misses 96 96 Partials 7 7 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SmartThingsOSS). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=SmartThingsOSS)

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