Update Redis lock to support Redis version < 5.0

Update the Redis lock connection intialization so that is works with
Redis versions < 5.0.

GitLab issue #709. Rob de Canha-Knight (@rssfed23) for the report
and debug information.

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/lock_manager/backends/redis_lock.py

@@ -18,7 +18,8 @@ class RedisLock(LockingBackend):
     def get_redis_connection(cls):
         redis_url = setting_backend_arguments.value.get('redis_url', None)
         server = redis.from_url(url=redis_url)
-        server.client_id()
+        # Force to initialize the connection
+        server.client()
         return server
 
     @classmethod