lock: handle refresh thread already started

vcsserver/lib/rc_cache/backends.py

@@ -306,6 +306,9 b' def get_mutex_lock(client, lock_key, loc'
                 return self.lock.acquire(wait)
             except redis_lock.AlreadyAcquired:
                 return False
+            except redis_lock.AlreadyStarted:
+                # refresh thread exists, but it also means we acquired the lock
+                return True
 
         def release(self):
             try: