Now `cinder-volume-worker` is set as DEFAULT.host. It results only
one host per volume service type registered regardless of replica
numbers.
To fix this, removed DEFAULT.host from default values so hostname
of pods will be used as host name.
It will produce garbage services with down state because pod name
changes every creation. To avoid this, added a cronjob for service
clean.
Change-Id: I9ec6f62105124f9088afdb231099b532fc83bb34
d554d74bf0