rtph264pay: Only mark the last fragment of an AU

Commit 4add820cce278213ede3d5fce427ea92e0619b6f removed the check for
the end of fragmentation. As a result, all fragments of an AU's last
NALU were marked.

Potential fix for https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/issues/540

gst/rtp/gstrtph264pay.c

@@ -965,7 +965,7 @@ gst_rtp_h264_pay_payload_nal (GstRTPBasePayload * basepayload,
 
       /* If it's the last fragment and the end of this au, mark the end of
        * slice */
-      gst_rtp_buffer_set_marker (&rtp, end_of_au);
+      gst_rtp_buffer_set_marker (&rtp, end && end_of_au);
 
       /* FU indicator */
       payload[0] = (nalHeader & 0x60) | 28;