Adding wait_for_resource_deletion function for volume cleanup
Adding wait_for_resource_deletion function for volume cleanup

I added a patch: https://review.openstack.org/#/c/308205/
that depends on this patch. The reason is “test_quota_usage” test
does not wait for volume deletion process to complete,
thus a volume is been deleted during my patch. To resolve
this issue I added delete_volume function to serve both tests
in order to prevent race condition.

Change-Id: Ie0f2739fbb4ee32e04dda508d922d0015b1a92a6

masayukig/tempest,sebrandon1/tempest,cisco-openstack/tempest,cisco-openstack/tempest,Tesora/tesora-tempest,Tesora/tesora-tempest,masayukig/tempest,vedujoshi/tempest,sebrandon1/tempest,bigswitch/tempest,bigswitch/tempest,Juniper/tempest,vedujoshi/tempest,Juniper/tempest,openstack/tempest,openstack/tempest