Change log level when L3 agent is disabled

Many times administrator don't set "debug=True" in production
environment. If that, we hardly find the root issue if L3 agent
doesn't work when someone disable some L3 agents.

So, change the log level from "debug" into "info" when L3 agent
is disabled.

Change-Id: Ibd5ca5c5479269c17d15b211652737611a5c4c40

neutron/db/l3_agentschedulers_db.py

@@ -371,8 +371,8 @@ def list_active_sync_routers_on_active_l3_agent(
         agent = self._get_agent_by_type_and_host(
             context, constants.AGENT_TYPE_L3, host)
         if not agentschedulers_db.services_available(agent.admin_state_up):
-            LOG.debug("Agent has its services disabled. Returning "
-                      "no active routers. Agent: %s", agent)
+            LOG.info(_LI("Agent has its services disabled. Returning "
+                         "no active routers. Agent: %s"), agent)
             return []
         scheduled_router_ids = self._get_router_ids_for_agent(
             context, agent, router_ids)