INT-3111 Fix Close Cached TCP Connection

A TCP Connection is closed when an outbound gateway times out.

However, with the CachingClientConnectionFactory, the connection
was returned to the pool instead of being physically closed.

Override forceClose() and physically close the connection so the
next time it is retrieved from the pool it is detected as stale
and re-established.

Refactor test case and invoke it twice; once with a regular connection
factory and once with a cached factory.

Remove an unused logger.