Automagically chkconfig --add custom initscripts

If a custom initscript does not show in /sbin/chkconfig --list, add it
when running any function that checks on/modifies the status of a
service. Saves the user from having to add a cmd.run state for each
custom initscript they deploy.

Service is disabled upon being added so that it does not run unless the
user turns it on, to avoid confusion.

Fulfills #2908, though I'll probably look into this for other service
providers as well.
Merge pull request #4195 from terminalmage/issue2908

Automagically chkconfig --add custom initscripts