Ignore hosts without stdout_lines in maas post-migrate
Ignore hosts without stdout_lines in maas post-migrate

If stdout_lines wasn't collected calling |sort on it will not produce
anything valuable for with_items (which expects a list or set). So we
need to make sure we default to an empty list in that case.

Addresses #545

xeregin/rpc-openstack,sigmavirus24/rpc-openstack,sigmavirus24/rpc-openstack,sigmavirus24/rpc-openstack,xeregin/rpc-openstack,cloudnull/rpc-openstack,jacobwagner/rpc-openstack,shannonmitchell/rpc-openstack,darrenchan/rpc-openstack,jacobwagner/rpc-openstack,prometheanfire/rpc-openstack,hughsaunders/rpc-openstack,darrenchan/rpc-openstack,sigmavirus24/rpc-openstack,cfarquhar/rpc-openstack,darrenchan/rpc-openstack,shannonmitchell/rpc-openstack,mancdaz/rpc-openstack,git-harry/rpc-openstack,rcbops/rpc-openstack,darrenchan/rpc-openstack,byronmccollum/rpc-openstack,byronmccollum/rpc-openstack,byronmccollum/rpc-openstack,mancdaz/rpc-openstack,git-harry/rpc-openstack,xeregin/rpc-openstack,busterswt/rpc-openstack,cfarquhar/rpc-openstack,stevelle/rpc-openstack,BjoernT/rpc-openstack,major/rpc-openstack,galstrom21/rpc-openstack,rcbops/rpc-openstack,busterswt/rpc-openstack,xeregin/rpc-openstack,claco/rpc-openstack,busterswt/rpc-openstack,major/rpc-openstack,BjoernT/rpc-openstack,robb-romans/rpc-openstack,cloudnull/rpc-openstack,prometheanfire/rpc-openstack,robb-romans/rpc-openstack,galstrom21/rpc-openstack,stevelle/rpc-openstack,stevelle/rpc-openstack,claco/rpc-openstack,hughsaunders/rpc-openstack,claco/rpc-openstack