Updated mdadm state to actually support style in docs.

Update docs in state to show both styles of defining opts.
Added destroy function to mdadm module to destroy an array
Added absent function to mdadm state
Removed unused import
Added some documentation back.
Merge pull request #4445 from shadowfax-chc/mdadm-absent

Mdadm absent
Corrected typo in modules/rh_service.py
Merge pull request #4447 from melinath/patch-1

Corrected typo in modules/rh_service.py
Fix support for GATEWAY in interface configs