compute api should throw exception if soft reboot invalid state VM

When user perform soft reboot to a VM which in suspended/paused/
stopped/error state, nova compute api should throw exception for
such state.

Change-Id: Ic365c6360f6b7407d9de0dac6ff1093484692cf4
Closes-Bug: #1236930
Merge "compute api should throw exception if soft reboot invalid state VM"