Add volume clone flag to clone tests

test_volumes_clone and test_volumes_clone_negative are cloning in
their tests, but don't have the volume clone tag in them for
disabling in Tempest. This patch adds the tag to both of these
tests.

Closes-Bug: 1615770

Change-Id: Iff0f1bd8996bb8aa982ee0f3373e7454221ae41e
2 files changed