Do not sync power state for new invalidated nodes

sync_power_state periodic task puts node in maintenance mode after max
sync retries. If node created and has unknown power state this
periodic task set maintenance mode too fast (there is not yet IPMI
credentials for example).
This patch prevent sync_power_state for these nodes if validate fail.

Closes-Bug: #1304642
Change-Id: I19798028adce91b107643f5419999389dafdccf3
Merge "Do not sync power state for new invalidated nodes"