Add hosts cleanup step for Beaker
Add hosts cleanup step for Beaker

This is necesarry when reprovisioning and hosts file state
can break idempotency.

Change-Id: If202e2c9663a472c087bdf1b2f6b74de83d3c2c1

redhat-openstack/infrared,okolisny/InfraRed,redhat-openstack/infrared,redhat-openstack/infrared,okolisny/InfraRed,okolisny/InfraRed