Comment 7 for bug 1257644

Maybe a red herring, but I'm suspicious of something going into nova recently which is maybe automatically disabling a host, or screwing something up in the set_host_enabled flow, these are the most recent changes in that path:

Change Ib4cc80e5: Add notification for host operation
Change Ib8d67838: Disable nova-compute on libvirt connectivity exceptions
Change Ia7544a35: Conditionalise automatic enabling of disabled host
Change I394e92fe: libvirt: Fix log message when disable/enable a host

I think it's got to be Ib8d67838 or Ia7544a35. Thinking is we have a libvirt connection hiccup which automatically disables the host and since tempest is running tests in parallel, it hits that window and the ComputeFilter doesn't return the host since it's automatically disabled, and then kaboom!