Allow partial connection to succeed

Xwayland can optionally be socket-activated by the Wayland compositor, in which case it would use only the sockets provided by the compositor.

However, that prevents other transport protocol from working, because when it's given a socket from the Wayland compositor, it would disable all other connections and rely solely on the given socket.

Change MakeAllCOTSServerListeners to allow for partial connections so that if partial is set to a non-zero value by the caller, we do not bail out in the address is already in use.

That allows the continue trying with other protocols even if the local conenction fails (as this is already handled by the socket from the Wayland compositor).

Related: xorg/xserver#817 (closed) Signed-off-by: Olivier Fourdan ofourdan@redhat.com