downloader: Release app when it fails
downloader: Release app when it fails

The downloader holds the app each time it downloads
content but only releases the app when it finishes
properly, causing the app not to close.

Release the app also when the download fails.

https://phabricator.endlessm.com/T17013

endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib