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 * Change the monitor message type names once again (hope this is
   the final version)
 * Pass -u (unbuffered) to sed to retain the actual output order in
   the log file
 * Fix a bug in helper code where the starting `{' was missing from
   the monitoring messages

This commit extendes the monitoring mechanism to include events from
snf-image-helper.

Trying to add a logical swap partition after an already existing logical
partition triggered an error in parted, because between logical partitions
a gap of at least 1 sector needs to be present.

Now FixPartitionTable task can enlarge logical partitions

Not all tasks, should be able to be excluded. If MountImage,
UnmountImage and InstallUnattanded are never excluded, then the system
deployment can't break. If you don't want to mount the image or install
Unattend.xml then you probably want to use EXCLUDE_ALL_TASKS, since all
other tasks depend on the aforementioned ones.

* In decode-properties.py, use subprocess.Popen method instead of
  subprocess.check_output, which is introduced in python 2.7

* Fix a bug in snf-image-helper where decode-properties.py was not
  properly called

* Fix a bug in FixPartitionTable task