Fix network poll() issue: don't interrupt poll if socket not connected. ...

Fix network poll() issue:  don't interrupt poll if socket not connected.  Listen sockets are not connected and the poll() is waiting for connection events.

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5717 42af7a65-404d-4744-a932-0658087f49c3