Avoid BadRequest error log on volume attachment
Avoid BadRequest error log on volume attachment

At the gate, only AttachVolumeNegativeTest makes nova-api output
error log as a negative test case like:

  ERROR nova.volume.cinder [None req-dcc8814f-7439-44c8-872e-86ea51f4b319
   tempest-AttachVolumeNegativeTest-431575524
   tempest-AttachVolumeNegativeTest-431575524]
   [instance: ca526f93-e723-4372-a1c1-4fa03ffc1bd7]
   Create attachment failed for volume 0a6e6a92-f095-4ab7-803c-826934824418.
   Error: Invalid volume: Volume 0a6e6a92-f095-4ab7-803c-826934824418 status
     must be available or downloading (HTTP 400)
     (Request-ID: req-5e5074ea-cd12-43ed-9355-5db539ca9720)
   Code: 400:
   BadRequest: Invalid volume: Volume 0a6e6a92-f095-4ab7-803c-826934824418
     status must be available or downloading (HTTP 400)
     (Request-ID: req-5e5074ea-cd12-43ed-9355-5db539ca9720)

Operators don't need to take care of BadRequest cases in general because
that is due to end user mistakes. So this patch makes nova-api avoiding
such error log case.

Closes-Bug: #1797237

Change-Id: I22d9d974822282ffc3c0942d4766b135717dd369

rahulunair/nova,klmitch/nova,rahulunair/nova,rahulunair/nova,mahak/nova,mahak/nova,klmitch/nova,openstack/nova,klmitch/nova,openstack/nova,klmitch/nova,openstack/nova,mahak/nova