fix(Makefile): upload fleetctl units all at once

Submitting and then starting systemctl units one-by-one
with fleet causes some issues because of dependencies -
if bar depends on foo, foo must be defined and started first.

This commit makes sure we always submit/start *all* units at
once, making this no longer order-dependent.

fixes #806
Merge pull request #807 from deis/fix_fleetctl_scheduling

fix(Makefile): upload fleetctl units all at once
chore(contrib/vagrant): update vagrant box to coreos-296.0.0