Log Message:
nginx: updated nginx_http_push_module to 1.2.8

1.2.8 (Apr. 12 2021)
 feature: nchan_subscriber_info locations for receiving customizable info from
      subscribers of a given channel.
 fix: incorrect lgging of disconnected subscribers with 400 error instead of 499
      (bug introduced in v1.2.7)
 feature: add $nchan_channel_subscriber_last_seen, $nchan_channel_subscriber_count
      and $nchan_channel_message_count variables
 fix: GCC 10 compatibility