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
Merge "Fix not attribute '_periodic_last_run'"