Avoid VM task state revert on instance termination

Related to bug 1046236.

Previously, if an exception is raised during the nova-compute node's
instance termination logic *before* the instance is evicted from the DB
(e.g. in the network teardown), then the task_state is reverted back to
None by the reverts_task_state decorator, so the instance continues
to be reported as ACTIVE with no outstanding task.

A subsequent attempt to delete the same instance results in the
quota_usages in_use count being decremented a second time.

This occurs despite I91a70ada as that fix depends on the VM task state
continuing to be DELETING. That logic was undermined in Id4358c50 which
caused the task state to be reverted on the successful or unsuccessful
conclusion of the action on the compute node.

Now, the motivation for Id4358c50 was to avoid the VM getting stuck with
a task state that prevents any further action other than deletion.
However in the case of a deletion already having been requested, this
protection is unnecessary and counter-productive. Hence we remove the
task state reversion from the terminate_instance action.

Change-Id: Ie5701e5c12f6241a203423d29d05df1858406c56

0 files changed, 0 insertions, 0 deletions