Add power_on flag to virt driver finish/revert migration methods

This patch adds a boolean power_on flag to the virt driver
finish_migration and finish_revert_migration methods to indicate whether
or not to power on the instance as part of the resize/migrate operation.
The default is to power on the instance.

Related to bug 1177811

Change-Id: I76c7d6912eda2c333554855a8956bd0fbb1e8b6d
Set resized instance back to original vm_state

You can resize an instance when it's in the ACTIVE or STOPPED state but
the code currently always finishes the resize (either confirmed or
rejected) by putting the instance into ACTIVE state. This change
saves the original vm_state and uses it to restore the state on the
instance after the resize is confirmed or rejected.

With this change, the resize flow will never automatically power on an
instance that is originally shutoff. The user, however, can manually
power on the resized instance to test it before confirming or rejecting
the resize. If the user powered on the instance and confirmed the
resize, then this change will leave the instance active. If the user
powered on the instance and then rejected the resize, this change will
stop the instance when it finishes the revert operation.

Related to bug 1177811

Change-Id: I19fa61d467edd5a7572040d084824972569ef65a
Merge "Add power_on flag to virt driver finish/revert migration methods"
Merge "Set resized instance back to original vm_state"