Merge branch 'devel-2.1'

* devel-2.1:
  QA, burnin: allow selection of reboot types
  Add a QA option to disable reboots during burnin

Conflicts:
	qa/qa-sample.json (trivial)
	qa/qa_cluster.py  (trivial)

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Luca Bigliardi <shammash@google.com>