My Http Live Streaming setup: Apache hosts the html, m3u8, and ts files
The ts files are copied over from http:devimages.apple.com/iphone/samples/bi
According to the HLS rfc documentation you should use "application/vnd.apple.mpegurl" or "audio/mpegurl" but you could also simply make the path end with .m3u8 or .m3u.
Each Playlist file MUST be identifiable either by the path component of its URI or by HTTP Content-Type. In the first case, the path MUST end with either .m3u8 or .m3u. In the second, the HTTP Content-Type MUST be "application/vnd.apple.mpegurl" or "audio/mpegurl". Clients SHOULD refuse to parse Playlists that are not so identified.
~ Chapter 4 of rfc8216, HTTP Live Streaming