Lots of fixes to revert S3ConfigFetcher to the previous version to avoid sending erroneous messages to the user and to use common code paths in dev and production, added more testable HttpClientFactory, added S3ConfigFetcher test, etc
Added error when we can't fetch and have no fallbacks
Removed redundant error message
Merge pull request #1488 from getlantern/s3config-errors

Fixes to S3Config fetching and messaging closes #1474 and closes #1475