fix feed path according to regression script

Originally committed as revision 13368 to svn://svn.ffmpeg.org/ffmpeg/trunk

tests/test.conf

@@ -52,7 +52,7 @@ CustomLog -
 # maximum size of the feed (100M bytes here). Default:
 # File=/tmp/feed_name.ffm FileMaxSize=5M
 
-File feed1.ffm
+File tests/feed1.ffm
 FileMaxSize 100M
 
 # Fire up ffmpeg pointing at this stream