h265parse: Consider SEI NALU as "HEADER" packets

Apply the commit 69c09c3

https://bugzilla.gnome.org/show_bug.cgi?id=754124
diff --git a/gst/videoparsers/gsth265parse.c b/gst/videoparsers/gsth265parse.c
index 79e3fa5..4832402 100644
--- a/gst/videoparsers/gsth265parse.c
+++ b/gst/videoparsers/gsth265parse.c
@@ -633,6 +633,7 @@
       if (!GST_H265_PARSE_STATE_VALID (h265parse, GST_H265_PARSE_STATE_GOT_SPS))
         return FALSE;
 
+      h265parse->header |= TRUE;
       /*Fixme: parse sei messages */
       /* mark SEI pos */
       if (h265parse->sei_pos == -1) {