Designate service_statuses is not working

When I set the 2 or more each designate service workers,
those service_status was not working.
In this case, The 'HeartBeatEmitter.start' is called
by child processes.
And The 'HeartBeatEmitter._emit_heartbeat' is called
by Parent process.
Parent process' '_running' value never change to TRUE
on parent process.
So in this case, designate isn't emitted the heartbeat.

Change-Id: I1338d2ca180274ae84d4b358ff467e6655eb8022
Closes-Bug: #1827070

designate/cmd/api.py

@@ -43,4 +43,5 @@ def main():
 
     server = api_service.Service(threads=CONF['service:api'].threads)
     service.serve(server, workers=CONF['service:api'].workers)
+    server.heartbeat_emitter.start()
     service.wait()

designate/cmd/central.py

@@ -40,4 +40,5 @@ def main():
 
     server = central.Service(threads=CONF['service:central'].threads)
     service.serve(server, workers=CONF['service:central'].workers)
+    server.heartbeat_emitter.start()
     service.wait()

designate/cmd/mdns.py

@@ -40,4 +40,5 @@ def main():
 
     server = mdns_service.Service(threads=CONF['service:mdns'].threads)
     service.serve(server, workers=CONF['service:mdns'].workers)
+    server.heartbeat_emitter.start()
     service.wait()

designate/cmd/pool_manager.py

@@ -60,4 +60,5 @@ def main():
     hookpoints.log_hook_setup()
 
     service.serve(server, workers=CONF['service:pool_manager'].workers)
+    server.heartbeat_emitter.start()
     service.wait()

designate/cmd/producer.py

@@ -48,4 +48,5 @@ def main():
 
     server = producer_service.Service(threads=CONF['service:producer'].threads)
     service.serve(server, workers=CONF['service:producer'].workers)
+    server.heartbeat_emitter.start()
     service.wait()

designate/cmd/worker.py

@@ -48,4 +48,5 @@ def main():
 
     server = worker_service.Service(threads=CONF['service:worker'].threads)
     service.serve(server, workers=CONF['service:worker'].workers)
+    server.heartbeat_emitter.start()
     service.wait()

designate/cmd/zone_manager.py

@@ -59,4 +59,5 @@ def main():
     server = producer_service.Service(
         threads=CONF['service:zone_manager'].threads)
     service.serve(server, workers=CONF['service:zone_manager'].workers)
+    server.heartbeat_emitter.start()
     service.wait()