install: cache the presets before evaluating

install: cache the presets before evaluating

The previous implementation traversed the various config directories,
walking the preset files and parsing each line to determine if a service
should be enabled or disabled. It did this for every service which
resulted in many more file operations than neccessary.

This approach parses each of the preset entries into an array which is
then used to check if each service should be enabled or disabled.