Add existing volumes when using pre-provisioned credentials
Add existing volumes when using pre-provisioned credentials

When using pre-provisioned credentials, the tenant may have volumes
other than those created in the testcase and so will make
test_volume_list_details_pagination and test_volume_list_pagination
fail unexpectedly. This is to fix it.

Change-Id: I997792dcf26a2ce07ec6e0de0b0557a0c260ea59
Closes-Bug: #1612097

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