stream-tcp: Change the connection name for pwindows.

As of now, when someone passes a punix:foo/bar as a connection type
in Windows, we create a TCP server using 127.0.0.1 and save the kernel
assigned port number in the file foo/bar. The connection name
as obtained through pstream_get_name() would be ptcp:127.0.0.1:$PORT.
This was okay if pstream_get_name() was only used for logging
purposes. But netdev-dummy uses it to close active connections when the
passed name and created name are different. This causes transient
connection teardowns while using patch ports in Windows unit tests
causing occasional packet loss.

This commit sets the connection name to be punix:foo/bar instead
of ptcp:127.0.0.1:$PORT for pwindows.

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