Merge branch 'devel-2.5'

* devel-2.5: (32 commits)
  PEP8 style fixes
  Wrap a few long lines
  listrunner: Avoid exception if machine is rebooted
  Remove wrong type declaration from option
  Fix wrong method name in cluster-merge
  Fix --skip-stop-instances help message
  cluster-merge: Add the --skip-stop-instances opt
  watcher: Wait for child processes by default
  Update release date in NEWS for 2.5.0~beta2
  Try 3 times before giving up on per-node commands
  Allow retrying commands in cluster-merge
  Add a TODO on the VerifyCluster option
  Transform node readd exceptions into just errors
  Offline node when adding it to a merged cluster
  Bump version to 2.5.0~beta2
  sphinx_ext: workaround epydoc warning
  check-news: Show per-file line number
  Unify some file headers
  Makefile: Add design-ovf-support to list of doc files
  ensure-dirs: Fix epydoc error
  ...

Reviewed-by: René Nussbaumer <rn@google.com>
Signed-off-by: Michael Hanselmann <hansmi@google.com>