Add support for adjusting etcd ttl on job_heartbeat. Switch the heartbeat method to a coroutine.

buildman/manager/basemanager.py

@@ -3,13 +3,15 @@ from trollius import coroutine
 class BaseManager(object):
   """ Base for all worker managers. """
   def __init__(self, register_component, unregister_component, job_heartbeat_callback,
-               job_complete_callback, public_ip_address):
+               job_complete_callback, public_ip_address, heartbeat_period_sec):
     self.register_component = register_component
     self.unregister_component = unregister_component
     self.job_heartbeat_callback = job_heartbeat_callback
     self.job_complete_callback = job_complete_callback
     self.public_ip_address = public_ip_address
+    self.heartbeat_period_sec = heartbeat_period_sec
 
+  @coroutine
   def job_heartbeat(self, build_job):
     """ Method invoked to tell the manager that a job is still running. This method will be called
         every few minutes. """