Stop the search once the slot for replication origin is found.

In replorigin_session_setup(), we were needlessly looping for
max_replication_slots even after finding an existing slot for the origin.
This shouldn't hurt us much except for probably large values of
max_replication_slots.

Author: Antonin Houska
Discussion: http://postgr.es/m/2694.1700471273@antos

src/backend/replication/logical/origin.c

@@ -1144,6 +1144,7 @@ replorigin_session_setup(RepOriginId node, int acquired_by)
 
 		/* ok, found slot */
 		session_replication_state = curstate;
+		break;
 	}