avformat/hls: return AVERROR_PROTOCOL_NOT_FOUND when http protocol is not available

Fixes compile error when building with network or protocols disabled.

This code would never be reached (because the demuxer fails much earlier on http playlists or segments), so it doesn't matter much what we do here as long as it compiles.

Signed-off-by: Aman Gupta <aman@tmm1.net>