Update Distributed-Poller.md (librenms#18583)

Clarify the text for Redis to avoid any ambiguity.

Author: dagbdagb

doc/Extensions/Distributed-Poller.md

@@ -52,6 +52,7 @@ REDIS_PASSWORD=PasswordGoesHere
 # If Redis ACLs are in use (recommended):
 REDIS_USERNAME=UsernameGoesHere
 ```
+Only the shared server points at 127.0.0.1. Other pollers point at the shared server's general IP address.
 
 ### Sentinel