Refine the error mechenism for remuxing.

[winlinvip]

When convert RTMP to HLS, if HLS error, should ignore and continue or error and reject RTMP connection? There is a configuration:

        # the error strategy. can be:
        #       ignore, disable the hls.
        #       disconnect, require encoder republish.
        #       continue, ignore failed try to continue output hls.
        # @see https://github.com/ossrs/srs/issues/264
        # Overwrite by env SRS_VHOST_HLS_HLS_ON_ERROR for all vhosts.
        # default: continue
        hls_on_error continue;

This is not good enough, and furthermore, when covert SRT to RTMP/RTC, what's the good strategy when RTMP or RTC error? We should design it carefully, to adapt for different use scenarios.

Please see #3392 (review) for where the issue comes from.