Call Rados.shutdown() explicitly before exit

This is mostly a demonstration of good behavior, as the resources will
be reclaimed on exit anyway.

Signed-off-by: Dan Mick <dan.mick@redhat.com>

src/ceph.in

@@ -877,4 +877,7 @@ def main():
     return 0
 
 if __name__ == '__main__':
-    sys.exit(main())
+    retval = main()
+    # shutdown explicitly; Rados() does not
+    cluster_handle.shutdown()
+    sys.exit(retval)