* stable-2.6: (21 commits)
  Release Ganeti 2.6.0 rc4
  Prepare NEWS for Ganeti 2.6.0rc4
  Add some rudimentary node group ipolicy checks
  Fix setting ipolicy on node groups
  Fix --no-headers for the new list-drbd command
  Add a simple QA test for gnt-node list-drbd
  Add a new gnt-node command list-drbd
  Implement a node to drbd minors query function
  Add a new unused confd query
  Add support for computing instance all/secondary nodes
  Add disk logical ID support in Objects.hs
  Fix a docstring in bdev's DRBD8 class
  Extend the Template Haskell loadFn model
  Change how customFields are built
  Implement lookup of partial names in Config.hs
  Reorganise the lookup functions
  Remove an unused function
  Ensure that disk.params is always defined (and a dict)
  Another small consistency fix with if branches
  Fix inconsistency in the LUXI protocol w.r.t. args
  ...

Conflicts:
        htools/Ganeti/HTools/QC.hs (imports changes, trivial)

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: René Nussbaumer <rn@google.com>