avformat/hlsenc: set default http method to PUT when method is null

avformat/hlsenc: set default http method to PUT when method is null

When the http method is not set, the method will use POST for ts,
PUT for m3u8, it is not unify, now set it unify.
This ticket id: #5315

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Reviewed-by: Moritz Barsnick <barsnick@gmx.net>
Signed-off-by: Steven Liu <lq@chinaffmpeg.org>