Repeatedly add log_filters,log_outputs to libvirtd.conf when restart

Change-Id: I14f07f3164f9201305ed1e94e9277a5a5792e850
Closes-bug: 1273058
Convert trove to plugin

Also adds an is_trove_enabled() function to match
https://review.openstack.org/69497 changes for is_service_enabled().

Change-Id: Ic0408ff6d9816aec8a3506931470470342a5dcd7
Merge "Repeatedly add log_filters,log_outputs to libvirtd.conf when restart"
Merge "Convert trove to plugin"