Destroy orig VM during resize if triggered by user

Patch I7598afbf0dc3c527471af34224003d28e64daaff introduces a
Minesweeper failure, due to the fact that it doesn't distinguish
between destroy operation triggered by the user and by the revert
resize.

This patch fixes the issue by checking the task state. If the task
state is revert_resize, the original VM doesn't get deleted.

Closes-Bug: #1376492

Change-Id: Idb9ac6c1ec5dcea52ce8e028f5cce08da1779321
(cherry picked from commit e464bc518e8590d59c2741948466777982ca3319)
Merge "Destroy orig VM during resize if triggered by user" into proposed/juno