Merge remote branch 'origin/devel-2.1'

* origin/devel-2.1:
  backend: Two small style fixes
  Allow cluster copy file over the replication net
  Enhance cli.GetOnlineNodes query/filtering
  Instance creation: implement --no-install mode
  Allow OS changes without reinstallation
  cmdlib: Abstract OS checks

Conflicts:
	lib/cli.py: Trivial

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>