Allow confirm_resize if instance is in 'deleting' status

Deleting an instance puts it into 'deleting' task_state.
If the instance is in 'resized' vm_status, this tries a
confirm_resize on the instance. confirm_resize currently expects
the task_state to be None. It should instead expect
None/deleting task_state.

Fixes bug: 1189391

Change-Id: I6a3f82eab9ed2242bfd38bc1ac760dbb4b3d8c4a
Merge "Allow confirm_resize if instance is in 'deleting' status"