Merge branch 'devel-2.6' into master

* devel-2.6:
  Improve error message when migration status fail
  Fix type error in kvm/GetMigrationStatus
  Fix PID file writing in Haskell daemons

Conflicts (both trivial):
        htools/Ganeti/Daemon.hs (_writePidFile rename)
        lib/hypervisor/hv_kvm.py (master fixed an indentation issue)

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>