Mark nova-baremetal driver as deprecated in Juno, removed in K

This removes the old "untested and soon to be replaced" warning
to be in init_host() like other drivers, and with more details
(i.e. a timeline).

Change-Id: I251cad65b7ccf66733d8a626b1a50bfa58456e7f
Merge "Mark nova-baremetal driver as deprecated in Juno, removed in K"