INT-3213 Fix Failing TCP Test

JIRA: https://jira.springsource.org/browse/INT-3212

TcpNioConnections can deadlock when a fixed thread pool is being used.
The deadlock is detected after 60 seconds, but the test case failed
after 20 seconds - before the deadlock was detected.

Change the test to use a cached thread pool instead.

Also, increase concurrency by using threading in the test server
so each socket is handled on a separate thread.

Enchance connectionId to include both local and remote ports to
aid debugging.

Some minor formatting corrections.