In our usage, we have one channel where we really care / want to know if it's down,
but also a bunch of other channels where they're expected to not be streaming most/all of the time.
To prevent these extra channels making a ton of noise, we introduce the concept of an "important"
channel, indicated by appending a '!' to the channel name in the command line.
So for example, you might specify channels as "foo! foo_backup foo_behindthescenes".
Important channels have the same behaviour as previously.
Non-important channels:
* Have a 20-second retry on a master playlist fetch failure, instead of 5
* Log at debug when the stream is down, instead of info.