checkout: change symlinked .gitmodules file test to expect failure

When dealing with `core.proectNTFS` and `core.protectHFS` we do check
against `.gitmodules` but we still have a failing test as the non-filesystem
codepath does not check for it.

tests/checkout/nasty.c

@@ -367,7 +367,12 @@ void test_checkout_nasty__symlink3(void)
 void test_checkout_nasty__gitmodules_symlink(void)
 {
 	cl_repo_set_bool(repo, "core.protectHFS", true);
+	test_checkout_fails("refs/heads/gitmodules-symlink", ".gitmodules");
+	cl_repo_set_bool(repo, "core.protectHFS", false);
+
 	cl_repo_set_bool(repo, "core.protectNTFS", true);
+	test_checkout_fails("refs/heads/gitmodules-symlink", ".gitmodules");
+	cl_repo_set_bool(repo, "core.protectNTFS", false);
 
-	test_checkout_passes("refs/heads/gitmodules-symlink", ".gitmodules");
+	test_checkout_fails("refs/heads/gitmodules-symlink", ".gitmodules");
 }