Correct the state for PAUSED instances on reboot

If an instance is in the PAUSED state before the compute node is
restarted, it will be left in an inconsistent state (impossible to
delete and/or restart it) after the node boots again.

This patch adds a check in the periodic task sync_power_state so when
this situation is detected the instance is stopped and left in a state
from where it can be started again or deleted.

Closes-Bug: #1265494
Change-Id: I7266ace596598522c28a3839091ef50faf4463c2
(cherry picked from commit 6abda5b738c5d801ede3328cf0ec1dc9dddc022f)
Merge "Correct the state for PAUSED instances on reboot" into stable/havana