Wait for power off before allocation tests

There is a race sometimes when power off persists after the allocation
query, causing it to fail[1].

[1] https://zuul.opendev.org/t/openstack/build/aab3ecc1f63f4a52b1015f726fd8d229

Closes-issue: https://mirantis.jira.com/browse/PRODX-9564
Change-Id: I2b854a3a6b0f40f46dfa030b84d58715572f3ad4
(cherry picked from commit 3fbd0a9d77d999bc633946889400f316a7e3e561)
1 file changed