My dear friend the TvHeadEnd Only stream https link or m3u Only not rtmp
Your channels, the videos you want to stream, you will HAVE to broadcast them to the rtmp address of Wowza.
Then, Wowza will encode and transcode it to m3u8, f4m, or else, and with various bitrates.
If TvHeadEnd cannot push the streams to a rtmp server, then you should change as Wowza only accepts RTMP as input.
So I'll repeat myself ;
1- Enable the transcoder on the admin panel.
2- Get your channels and stream them to the rtmp address of Wowza server (from whatever software you want to use).
3- Wowza will encode, transcode, and give you the output m3u8, f4m or else that you want (in http and with various bitrates).