tests: print errors from ffserver

Not doing so makes debugging unnecessarily hard.
Reviewed-by: Reynaldo H. Verdejo Pinochet <reynaldo@osg.samsung.com>
Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Cadhalpun <Andreas.Cadhalpun@googlemail.com>

tests/ffserver-regression.sh

@@ -12,7 +12,7 @@ target_path=$5
 FILES=$(sed -n 's/^[^#]*<Stream \(.*\)>.*/\1/p' $2 | grep -v html)
 
 rm -f tests/feed1.ffm
-$target_exec ${target_path}/ffserver${PROGSUF} -d -f "$2" 2> /dev/null &
+$target_exec ${target_path}/ffserver${PROGSUF} -d -f "$2" &
 FFSERVER_PID=$!
 echo "Waiting for feeds to startup..."
 sleep 2