Convert the value to int type only if it exists in CLIENT INFO (#3688)

Currently, client info will try to convert the set of keys to the int type
without checking if it exists or not. For example, both `argv-mem` and `tot-mem`
are introduced in 6.2, and force converting an non-existent value might
cause an exception in older or newer versions. To keep the compatibility with the older/newer
Redis server, we could just convert it only if the key exists.

Author: git-hulk

redis/_parsers/helpers.py

@@ -676,7 +676,8 @@ def parse_client_info(value):
         "omem",
         "tot-mem",
     }:
-        client_info[int_key] = int(client_info[int_key])
+        if int_key in client_info:
+            client_info[int_key] = int(client_info[int_key])
     return client_info