Moved registration of lifcycle events handler in init_host()

The callback for handling lifecycle events now gets registered
before libvirt version is checked.  This is necesary because the
callback must be registered before the first time the connection
to libvirt is used.

Closes-bug: #1220278.

Change-Id: Id3a06c497d088078b4ea678ec9dde23bf0f406d4
Merge "Moved registration of lifcycle events handler in init_host()"