Don't cache anything in Zookeeper implementation (#2909)

Cache creates a lot of problems and prevents implementing a feature of automatic retention of physical replication slots for members with configurable retention policy.

Just read the entire cluster from Zookeeper instead and use watchers only for the `/leader` and `/config` keys.

features/environment.py

@@ -692,7 +692,7 @@ class ZooKeeperController(AbstractExternalDcsController):
         self._client = kazoo.client.KazooClient()
 
     def process_name(self):
-        return "zookeeper"
+        return "java .*zookeeper"
 
     def query(self, key, scope='batman', group=None):
         import kazoo.exceptions