libvhost-user-glib: fix VugDev main fd cleanup

libvhost-user-glib: fix VugDev main fd cleanup

If you try to make a device implementation that can handle multiple
connections and allow disconnections (which requires overriding the
VHOST_USER_NONE handling), then glib will warn that we remove a src
while it's still on the mainloop, and will poll() an FD that doesn't
exist anymore.

Fix this by making vug_source_new() require pairing with the new
vug_source_destroy() so we can keep the GSource referenced in the
meantime.

Note that this requires calling the new API in vhost-user-input.
vhost-user-gpu also uses vug_source_new(), but never seems to free
the result at all, so I haven't changed anything there.

Fixes: 8bb7ddb78a1c ("libvhost-user: add glib source helper")
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Message-Id: <20200123081708.7817-3-johannes@sipsolutions.net>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>