Fix search disk name for the config_drive in scenario test
Fix search disk name for the config_drive in scenario test

This commit fixes search for config_drive device name in
test "verify_metadata_on_config_drive", that supports only lowercase.
It needs because "mkfs" tool, for example in RHEL, capitalize the label
for config_drive ("CONFIG-2" instead of "config-2"), that used
in test as filter for blkid.

Closes-Bug: #1596868
Change-Id: I09684a7a295ea12ac372aadac926fe34708a66d4

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