osmux: Use available API to check if remote end is known

Since recently the port is guaranteed to be placed at
CRCX/MDCX in the sockaddr, hence we can check it using the API instead
of checking manually only for the address part.

In osmux_send_dummy() we actually fix a bug where an in_addr was being
compared against a struct sockaddr.

Change-Id: I736e7f4c51e577d8eb0b96bc776f984f928b6d27
1 file changed