rpc: avoid leak of GSource in use for interrupting main loop

We never release the reference on the GSource created for
interrupting the main loop, nor do we remove it from the
main context if our thread is woken up prior to the wakeup
callback firing.

This can result in a leak of GSource objects, along with an
ever growing list of GSources attached to the main context,
which will gradually slow down execution of the loop, as
several operations are O(N) for the number of attached GSource
objects.

Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

src/rpc/virnetclient.c

@@ -1946,7 +1946,7 @@ static int virNetClientIO(virNetClient *client,
     /* Check to see if another thread is dispatching */
     if (client->haveTheBuck) {
         /* Force other thread to wakeup from poll */
-        GSource *wakeup = g_idle_source_new();
+        g_autoptr(GSource) wakeup = g_idle_source_new();
         g_source_set_callback(wakeup, virNetClientIOWakeup, client->eventLoop, NULL);
         g_source_attach(wakeup, client->eventCtx);
 
@@ -1968,6 +1968,7 @@ static int virNetClientIO(virNetClient *client,
             return -1;
         }
 
+        g_source_destroy(wakeup);
         VIR_DEBUG("Woken up from sleep head=%p call=%p",
                   client->waitDispatch, thiscall);
         /* Three reasons we can be woken up