Fix build with polkit0

Commit 8dd623b9 introduced a build error with --enable-compile-warnings=error

  remote.c:2593: error: unused variable 'rv' [-Wunused-variable]

Pushing under build-breaker rule.

daemon/remote.c

@@ -2590,7 +2590,6 @@ remoteDispatchAuthPolkit(virNetServerPtr server,
     DBusError err;
     const char *action;
     char *ident = NULL;
-    int rv = -1;
     struct daemonClientPrivate *priv =
         virNetServerClientGetPrivateData(client);