Currently, autostart for libvirt default network is disabled only when
this network is active during nova playbook execution.
It's an incorrect behavior because in some cases this network may not be
active from the beginning.
Autostart should be always disabled to ensure that this network will not
be unexpectedly marked as active in the future(during package upgrade,
host reboot etc.).
Closes-Bug: #2042369
Change-Id: I697234bda1601b534ce1b6ab186fa98f83179ee8
feb15af75b