Fix retained msgs not sent by bridges.

This occurred when a bridge connected for the first time and so made a
local subscription for outgoing topics.

Closes #701.

ChangeLog.txt

@@ -4,6 +4,8 @@
 Broker:
 - Elevate log level to warning for situation when socket limit is hit.
 - Remove requirement to use `user root` in snap package config files.
+- Fix retained messages not sent by bridges on outgoing topics at the first
+  connection. Closes #701.
 
 Build:
 - Various fixes to ease building.

src/bridge.c

@@ -145,6 +145,9 @@ int bridge__connect_step1(struct mosquitto_db *db, struct mosquitto *context)
 		if(context->bridge->topics[i].direction == bd_out || context->bridge->topics[i].direction == bd_both){
 			log__printf(NULL, MOSQ_LOG_DEBUG, "Bridge %s doing local SUBSCRIBE on topic %s", context->id, context->bridge->topics[i].local_topic);
 			if(sub__add(db, context, context->bridge->topics[i].local_topic, context->bridge->topics[i].qos, &db->subs)) return 1;
+			sub__retain_queue(db, context,
+					context->bridge->topics[i].local_topic,
+					context->bridge->topics[i].qos);
 		}
 	}
 
@@ -308,6 +311,9 @@ int bridge__connect(struct mosquitto_db *db, struct mosquitto *context)
 		if(context->bridge->topics[i].direction == bd_out || context->bridge->topics[i].direction == bd_both){
 			log__printf(NULL, MOSQ_LOG_DEBUG, "Bridge %s doing local SUBSCRIBE on topic %s", context->id, context->bridge->topics[i].local_topic);
 			if(sub__add(db, context, context->bridge->topics[i].local_topic, context->bridge->topics[i].qos, &db->subs)) return 1;
+			sub__retain_queue(db, context,
+					context->bridge->topics[i].local_topic,
+					context->bridge->topics[i].qos);
 		}
 	}