t3701: ensure correctly set up repository after skipped tests

There are two tests that are skipped if file modes are not obeyed by the
file system. In this case, the subsequent test failed because the
repository was in an unexpected state. This corrects it.

Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t3701-add-interactive.sh

@@ -165,6 +165,12 @@ test_expect_success FILEMODE 'stage mode but not hunk' '
 
 # end of tests disabled when filemode is not usable
 
+test_expect_success 'setup again' '
+	git reset --hard &&
+	test_chmod +x file &&
+	echo content >>file
+'
+
 # Write the patch file with a new line at the top and bottom
 cat >patch <<EOF
 index 180b47c..b6f2c08 100644