Resolves #15537 malformed mdadm.conf lines
Added logic for updating existing config lines
Corrected logic for multiple raid volumes
Made ubuntu bug work around a bit more robust
Removed dict comprehension for python 2.6 compat

Boy it sure would be nice if we didn't have to keep compatibility with
python versions from 5 years ago :)
Merge pull request #15549 from drawks/iss15537

Resolves #15537 malformed mdadm.conf lines