Improve hls VOD mode hls performance problem.

This fixes the creation of the hls manifest in hlsenc.c by writing the
entire manifest at the end for VOD playlists. Live & Event Playlists are unaffected.
This also fixes the behavior with HLS_TEMP_FILE to work correctly when
-hlsflags temp_file is specified, instead of always relying on use_rename, which caused these problems.

Files that would previously take over a week to fragment now take
1 minute on the same hardware. This was a 153 hour audio file (2.2GB of audio).

Signed-off-by: Ronak Patel <ronak2121@yahoo.com>