engine: blank template no need default vm_init

By having a default vm_init all inherit VMs are getting blank vm_init as
well.

Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1155951
Change-Id: Ifa39cad168d523f1a902095b28cde91bf49f14db
Signed-off-by: Shahar Havivi <shaharh@redhat.com>