INT-2901 Add Namespace Prefix

Avoid confusion with the core header enricher.
Fix Syslog Test

Test didn't wait for the TCP server to start listening.
INT-3087:Fix MongoDbMessageStore RemoveMessage Bug

Add new query so the same message found in pollMessageFromGroup is the
one which gets deleted.

See jira for more details: https://jira.springsource.org/browse/INT-3087

INT-3087 Polishing

Use an atomic method in pollMessageFromGroup to pop the first message.

Add test cases for pollMessageFromGroup and removeMessageFromGroup
where the same message exists in multiple groups.
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.