socket-util: Log the kernel assigned port number when asked.

socket-util: Log the kernel assigned port number when asked.

So far, we log the kernel assigned port number when the port number is
not specified. On Windows, this happens multiple times because "unix"
sockets are implemented internally via TCP ports. This means that many tests,
specially the ovs-ofctl monitor tests, need to filter out the
additional messages. Doing that is not a big deal, but I think it will
keep manifesting in future tests added by Linux developers.

With this commit, we simply don't print the kernel assigned TCP ports
on Windows when done for "unix" sockets.

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>