Move verify-ipv6-only-deployments

from Tempest to DevStack as it tests DevStack side of things and
is useful for projects not using Tempest.

This is part 2 of 2.
The 1st part is DevStack-side, in Depends-On.

The script is left calling out to devstack because legacy (dsvm)
jobs rely on its presence.

Depends-On: Ie166730843f874b9c99e37244e460d7ad33b7eeb
Change-Id: I6fa17ae413f106453303c4882925573bd8e05029
diff --git a/playbooks/devstack-tempest-ipv6.yaml b/playbooks/devstack-tempest-ipv6.yaml
index 4788362..d56fb73 100644
--- a/playbooks/devstack-tempest-ipv6.yaml
+++ b/playbooks/devstack-tempest-ipv6.yaml
@@ -15,5 +15,5 @@
     # IPv6 only env for example Devstack IPv6 settings and services listen
     # address is IPv6 etc. This is invoked before tests are run so that we can
     # fail early if anything missing the IPv6 settings or deployments.
-    - ipv6-only-deployments-verification
+    - devstack-ipv6-only-deployments-verification
     - run-tempest