Replace live playlist sliding warnings with improved logging

[robwalch]

This PR will...

Cleanup alignPlaylists in base-stream-controller. This makes it clear why alignStream is being called. Logging is only performed after a call to alignStream with pertinent information.

Why is this Pull Request needed?

Warnings were being logged on stream start that did not merit that level of logging. The three different logger messages were not always very helpful or informative.

With these changes we'll only see logs when:

1. There are not fragments (this does merit a warning if an error hasn't already occurred)
2. Action was taken to align the stream after a refresh or first switch to a new level

Resolves issues:

Resolves #3933

Checklist

• changes have been done against master branch, and PR does not conflict