Added unit test of JmxConnectionParams to validate hypothesis of issue #190.

Short story, seems that hashCode() implementation is good, at least in HEAD.
Added unit test of JmxConnectionParams to validate hypothesis of issue #190.

Also added tests for equals() method while I'm at it ...
Merge pull request #192 from jmxtrans/jmx-remote-pool-not-reusing-connections

Added unit test of JmxConnectionParams to validate hypothesis of issue #190.