Don't allow reboot when instance in rebooting_hard

It shouldn't allow reboot a instance while the instance in
rebooting_hard task state.
If the instance is in rebooting_hard, solf reboot action is
meaningless.

Change-Id: I43147104a7473eaaf1b86f84386bb28b7e3574c3
Closes-bug: #1288926
Merge "Don't allow reboot when instance in rebooting_hard"