systemd: try harder to bind to notify socket

systemd: try harder to bind to notify socket

Without the socket open we are going to crash and burn. If for
whatever reason we fail during deserialization we will fail when
trying to open the socket. In this case it is better to unlink the old
socket and maybe lose some messages, than to continue without the
notification socket.

Of course this situation should not happen, but we should handle
it as gracefully as possible anyway.

https://bugzilla.redhat.com/show_bug.cgi?id=1099299