Merge remote branch 'origin/devel-2.1'

* origin/devel-2.1:
  Explicitely return None from IgnoreSignals
  AsyncUDPSocket: fix IgnoreSignals usage and test
  Add KVM chroot feature
  Fix and Improve TryToRoman unittest

Conflicts:
	test/ganeti.daemon_unittest.py
	  - trivial

Signed-off-by: Guido Trotter <ultrotter@google.com>
Reviewed-by: Michael Hanselmann <hansmi@google.com>