avformat/hlsenc: resend full url of the init fragment mp4

fix ticket: 8651
because the init fragment mp4 file name is without base url name,
so just modify it use the full url which splice after init function.

Tested-by: matclayton
Signed-off-by: Steven Liu <liuqi05@kuaishou.com>

libavformat/hlsenc.c

@@ -2274,7 +2274,7 @@ static int hls_init_file_resend(AVFormatContext *s, VariantStream *vs)
     int ret = 0;
 
     set_http_options(s, &options, hls);
-    ret = hlsenc_io_open(s, &vs->out, hls->fmp4_init_filename, &options);
+    ret = hlsenc_io_open(s, &vs->out, vs->base_output_dirname, &options);
     av_dict_free(&options);
     if (ret < 0)
         return ret;