Named return variables should only be used to describe the returned type
further, e.g. `err error` doesn't add any new information and is just
stutter.
Remove special tags necessary for gmond and runit collectors. All
collectors get built. Selection of which collectors to use continues to
happen via parameter.
Switch to Update using the Collecter Collect interface, due to not knowing all
metricnames in all modules beforehand we can't use Describe and thus the full
Collecter interface.
Remove 'updates', it's meaning varies by module and doesn't add much.
This collector exports the following metrics:
- raid_drive_temperature: drive temperature
- raid_drive_count: drive error and event counters
- raid_adapter_disk_presence: disk presence per adapter
