Replace start_guests with resume_guests

Fuel UI offers an option to "start guests on reboot" which,
if set to true, will attempt to restart all guests on a
given host regardless of prior status. This commit changes
the nova.conf entry from start_guests_on_boot to
resume_guets_state_on_host_boot.

Depends on https://review.openstack.org/#/c/124207/ in fuel-library

Change-Id: Ib7515b760fff08226de887748e611030ae101a50
Partial-Bug: #1352284
Merge "Replace start_guests with resume_guests"