HLS: Support disable variant for HLS Edge Cluster.

[winlinvip]

If using HLS Edge Cluster, such as NGINX for HLS distribution, then HLS variant cannot be enabled. This will cause each client requesting m3u8 to go back to the origin server, resulting in a significant load on the origin server and preventing scalability.

TRANS_BY_GPT3

[winlinvip]

It seems that the timeout for detecting HLS client cannot be configured.

TRANS_BY_GPT3

[winlinvip]

Fixed in e027d28

        # For HLS pseudo streaming, whether enable the session for each TS segment.
        # If enabled, SRS HTTP API will show the statistics about HLS streaming bandwidth, both m3u8 and ts file. Please
        # note that it also consumes resource, because each ts file should be served by SRS, all NGINX cache will be
        # missed because we add session id to each ts file.
        # Note that it will make NGINX edge cache always missed, so never enable HLS streaming if use NGINX edges.
        # Default: on
        hls_ts_ctx on;