[munin/f21] (3 commits) ...Backporting 2.1 fixes

[fenris02]

Summary of changes:

  93a379a... RHBZ# 1170164: add tmpfs/devtmpfs to df exclude list (*)
  4db6b61... Backporting 2.1 changes (*)
  b8fb6c5... Backporting 2.1 fixes (*)

(*) This commit already existed in another branch; no separate mail sent