nathelper: set the max partition for keepalives in usrloc

- used to distribute registration records for db only mode in usrloc

modules/nathelper/nathelper.c

@@ -675,6 +675,7 @@ mod_init(void)
 			LM_ERR("bad config - natping_processes must be >= 0\n");
 			return -1;
 		}
+		ul.set_max_partition(natping_processes*natping_interval);
 
 		sipping_flag = (sipping_flag==-1)?0:(1<<sipping_flag);
 		natping_disable_flag = (natping_disable_flag==-1)?0:(1<<natping_disable_flag);