Readd memcached concurrency (#1019)

Author: Dreamsorcerer

tests/performance/test_concurrency.py

@@ -12,8 +12,7 @@
 set_start_method("spawn")
 
 
-# TODO: Fix and readd "memcached" (currently fails >98% of requests)
-@pytest.fixture(params=("memory", "valkey"))
+@pytest.fixture(params=("memcached", "memory", "valkey"))
 def server(request):
     p = Process(target=run_server, args=(request.param,))
     p.start()