Fix not attribute '_periodic_last_run'

The ConductorManager class wasn't calling __init__ from
its parent object, causing an AttributeError exception
to be raised when accessing the attribute _periodic_last_run.
This attribute was initialized in the PeriodicTasks class.

Change-Id: Ieb850bf448f4b04be33c2cfecbac2de5925d6fda
Closes-Bug: #1351114

ironic/conductor/manager.py

@@ -138,6 +138,7 @@ class ConductorManager(periodic_task.PeriodicTasks):
     target = messaging.Target(version=RPC_API_VERSION)
 
     def __init__(self, host, topic):
+        super(ConductorManager, self).__init__()
         if not host:
             host = CONF.host
         self.host = host