NovaCompute: Fix loop on start checking for evacuate attribute
NovaCompute: Fix loop on start checking for evacuate attribute

The loop only waits for the evacuate attribute to be changed to no, but
we should also check if the evacuate attribute is gone (in case the user
does this manually).

Change-Id: I8d5c5830da07864ee748209be55fda506b1be585

openstack/openstack-resource-agents