Always use correct host for aggregates test suite

This is to always select the correct host for adding and removing
a host to and from an aggregate to make it consistent with the
Tempest implementation which should work for any cloud deployment
[0].

[0] https://github.com/openstack/tempest/blob/8f323f3dab5a9316170c614c77d621d1078e627a/tempest/api/compute/admin/test_aggregates.py#L42

Change-Id: I62224b28ea8347b66856b0c3812f4c1db2cdde41
1 file changed