fate-run: use 'run' function in 'ffmpeg' function

Originally committed as revision 24837 to svn://svn.ffmpeg.org/ffmpeg/trunk

tests/fate-run.sh

@@ -45,7 +45,7 @@ run(){
 }
 
 ffmpeg(){
-    $target_exec $target_path/ffmpeg -v 0 "$@"
+    run ffmpeg -v 0 "$@"
 }
 
 framecrc(){