hlssink: do not lose ref to the multifilesink

It is needed to update location properties and it was being lost on
state changes, causing issues if the pipeline was to be reused

ext/hls/gsthlssink.c

@@ -196,10 +196,6 @@ gst_hls_sink_reset (GstHlsSink * sink)
   sink->count = 0;
   sink->timeout_id = 0;
   sink->last_running_time = 0;
-  /* we don't need to unref since we gst_bin_add-ed multifilesink
-   * to ourselves
-   */
-  sink->multifilesink = NULL;
   sink->waiting_fku = FALSE;
   gst_event_replace (&sink->force_key_unit_event, NULL);
   gst_segment_init (&sink->segment, GST_FORMAT_UNDEFINED);