gdbus-connection: Fix race condition in test

The test was expecting that the spawned process wouldn't start
up before the NameOwnerChanged signal was subscribed.
gcleanup: A bit of cleanup and reorg

 * s/G_CLEANUP_MODULE/G_CLEANUP_SCOPE/
 * Change args for g_type_cleanup_push()
 * Explicit about what G_CLEANUP_DEFINE is defining
gdbusintrospection: Free up cache when done with it
gdbusserver: Simpler reffing of new connections
gdbusname: Cleanup global tables
gdbusprivate: Shutdown shared worker thread correctly

Both when idle and during cleanup.
gtestdbus: Don't destroy GSource twice
gtestdbus: Properly close server connections

Otherwise g_test_dbus_down() following a g_test_dbus_stop()
will hang until it times out.
gtestdbus: Fix leak of GMainLoop
gtestdbus: Cleanup io channel which would otherwise leak
gdbus-auth: Fix leaks in tests
gdbus-connection-slow: Fix leak in tests
gdbus-connection: Fix leaks in tests
gdbus-example-export: Fix behavior when using cleanup
gdbus-export: Fix leaks in tests
gdbus-introspection: Fix leaks in tests
gdbus-proxy: Fix erroneous timeout during following tests
gdbus-testserver: Fix behavior during cleanup
gtestutils: More cleanup
asyncqueue-test: Fix leaks in tests