Merge branch 'stable-2.8' into stable-2.9

Merge branch 'stable-2.8' into stable-2.9

* stable-2.8
  Version bump for 2.8.4 and NEWS update
  Update NEWS file with news about job cancellation bugfix
  Fix QA flakiness
  Linting fix: remove unused import
  Add missing parameter entry to man file
  Add QA test for job cancellation
  Add correct locking of master node to gnt-debug delay
  Add job id type assert to jqueue.py
  Add job id transformation/check to Luxi Python client
  Start-master/stop-master always fail if confd is disabled
  Improve backwards compatibility of Issue 649 fix
  Add missing NEWS entries from stable-2.8
  Change usb_devices separator to whitespace

Conflicts:
	NEWS: take both additions
	configure.ac: ignore revision bump
	lib/cmdlib/test.py: manually redo changes of stable-2.8
	    on stable-2.9 version

Signed-off-by: Klaus Aehlig <aehlig@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>