This patch brings two somewhat related changes:
1. Older versions of VirtualBMC worked without any server keeping
state on the filesystem. The contemporary version is build around
client-server model. To preserve backward compatibility, the
`vbmc` client would invoke `vbmcd` behind the scenes if the daemon
is not running.
This change inhibits this automatic `vbmcd` start behaviour because
devstack invokes `vbmcd` explicitly through systemd.
2. This patch makes Devstack messing with VirtualBMC only if it is
determined that IPMI deployment is required. Otherwise (e.g.
Redfish deployment is planned) Devstack will not attempt to
start/stop IPMI emulation.
Change-Id: Id9a2ed71a997fb13523a77563d6e941904675f97
01b0be9db2