INT-3146 TCP SO Timeout with Caching Client CF

https://jira.springsource.org/browse/INT-3146

Incompatibility of using socket timeouts with a caching client
connection factory.

When a socket option timeout (soTimeout) is set on a TCP connection
and the timeout occurs, the socket is closed.

When a connection is intercepted, the close is performed through
the interceptor (for example to allow a closing handshake before the
physical close).

However, the caching client connection factory is implemented
using an interceptor, which returns the underlying connection to
the cache pool (for reuse). In the case of a TcpNetConnection,
the reader thread has terminated meaning that, the next time the connection
is used, no reply will ever be received.

The work-around (when using a gateway) is to use the 'remote-timeout'
attribute instead of relying on the soTimeout. There is no
work around when using collaborating channel adapters with a Net
connection. Using NIO works because there is no reader thread
in that case, but the socket is never closed on a timeout.

Add a boolean 'timedOut' property to AbstractTcpConnection which the caching
connection factory can use to determine whether a physical close
of the connection is required.

Add test cases for Net and NIO implementations.

Conflicts:

	spring-integration-ip/src/main/java/org/springframework/integration/ip/tcp/connection/AbstractTcpConnection.java
	spring-integration-ip/src/test/java/org/springframework/integration/ip/tcp/connection/CachingClientConnectionFactoryTests.java