Correct policy names for volume metadata tests

This PS accomplishes 2 things:

1) Correct policy name for volume metadata tests that have the
wrong name. They are:
  * "volume:update_volume_metadata" ->
    "volume_extension:volume_image_metadata" [0]
  * "volume:delete_volume_metadata" ->
    "volume_extension:volume_image_metadata" [0]
2) Group together both the "volume_extension:volume_image_metadata"
   policy tests for easier readability/maintenance.\
3) Add cleanups to both tests.

[0] https://github.com/openstack/cinder/blob/0ac4af182fdd55d4a97ce283070f7b8e6480540f/cinder/policies/volume_metadata.py#L98
[1] https://github.com/openstack/cinder/blob/0ac4af182fdd55d4a97ce283070f7b8e6480540f/cinder/policies/volume_metadata.py#L106

Change-Id: Ie110283eca9decc37741b6197d0eb3f11d8918e9
1 file changed