tests: fix memleak when destroying test server

tests/wp/test-server.h

@@ -41,4 +41,5 @@ wp_test_server_teardown (WpTestServer *self)
   pw_thread_loop_stop (self->thread_loop);
   pw_context_destroy (self->context);
   pw_thread_loop_destroy (self->thread_loop);
+  g_free (self->name);
 }