Updated openstack/openstack
Project: openstack/nova  6b7aae5b8d5da5144d8ef9b9c8fb83a0b98ac2c9
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XenAPI: Speedup host_ref cannot change - get it once

The host we run on is fixed - getting this each time from XAPI
is expensive

Change-Id: Ifee9a778f3ed855ef52b001de3fc2ebbd0b972cf