Add status mapping for shutoff instance when resize

Current code always map instance's status into Shutoff when
getting status of resizing instance with power_state shutoff.
This isn't consistent with active instance, we should add
status mapping for power-off resizing instance.

Closes-Bug: #1247106
Co-Authored-By: chenxiao <chenxiao@cn.ibm.com>
Change-Id: Id4bff71b2c46ec9dccea6d8ac36eba273e48ea5d
Merge "Add status mapping for shutoff instance when resize"