avformat/http: copy only mime type from Content-Type

Content-Type can include charset and boundary which is not a part of
mime type and shouldn't be copied as such.

Fixes HLS playback when the Content-Type includes additional fields.
Signed-off-by: Kacper Michajłow <kasper93@gmail.com>

libavformat/http.c

@@ -1205,7 +1205,7 @@ static int process_line(URLContext *h, char *line, int line_count)
             }
         } else if (!av_strcasecmp(tag, "Content-Type")) {
             av_free(s->mime_type);
-            s->mime_type = av_strdup(p);
+            s->mime_type = av_get_token((const char **)&p, ";");
         } else if (!av_strcasecmp(tag, "Set-Cookie")) {
             if (parse_cookie(s, p, &s->cookie_dict))
                 av_log(h, AV_LOG_WARNING, "Unable to parse '%s'\n", p);