Merge branch 'stable-2.6' into devel-2.6

* stable-2.6:
  Fix opcode validation for OpOobCommand.command
  Fix typo in manpage for gnt-os
  gnt-instance.8: Add index to disk and nic removal

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