Fix up stderr handling in bench runs.

Send stderr to the  $FULL file, not inline with stdout.

common.bonnie

@@ -12,7 +12,7 @@ run_bonnie()
 	rm -fr ./bonnie
 	[ $status -ne 0 ] && exit 1
 	filter_stdout < $tmp/bonnie.stdout
-	filter_stderr < $tmp/bonnie.stderr
+	filter_stderr < $tmp/bonnie.stderr 1>&2
 	rm -f $tmp/bonnie.stdout $tmp/bonnie.stderr
 	exit 0
 }