Set explicit zk session timeout in nerve

[gmcatsf]

Summary

Current nerve does not specify explicit value for session timeout. By default ruby client uses RECEIVE_TIMEOUT=10000ms which leads to 20-sec session in zk server.

https://github.com/zk-ruby/zookeeper/blob/master/ext/c_zookeeper.rb#L20

The change adds receive_timeout_msec=16000 when creating zk client and will set session timeout to be 32-sec. This value will be different from other clients making it possible to identify nerve connections/sessions.

Test

• unit tests: bundle exec rspec
• To verify that zk session is set to 32-sec, manual integration test was executed with zk server:
  • created an instance of Nerve::Reporter::Zookeeper connecting to test zk server.
  • use 4-letter commands to dump connections on zk server: echo cons | nc localhost 2181 > cons.txt
  • output shows that test connection has 32-sec session with to=32001: /172.18.26.75:62059[1](queued=0,recved=3,sent=3,sid=0x66055392eb24038d,lop=CREA,est=1594229429532,to=32001,lcxid=0x5f0602b6,lzxid=0xb50009c930,lresp=22937508907,llat=0,minlat=0,avglat=0,maxlat=0)

Reviewers

@panchr @austin-zhu @Jason-Jian

[gmcatsf]

Updated version to 0.9.7

[gmcatsf]

@panchr could you pls merge it as I do not have write access?