rollback with correct bootmode
Merge branch 'fix_snap_rollback_gui' of github.com:StefanScherer/vagrant-multiprovider-snap into StefanScherer-fix_snap_rollback_gui

Conflicts:
	lib/vagrant-multiprovider-snap/providers/vmware_fusion/driver/base.rb
	lib/vagrant-multiprovider-snap/providers/vmware_workstation/driver/base.rb
Use providers' start() methods instead of vmrun

Will be more compatible if the provider changes in future.
Merge branch 'StefanScherer-fix_snap_rollback_gui'