pam/integration-tests: Use a shared authd instance only in race mode by default

In case, the env variable AUTHD_TESTS_USE_SHARED_AUTHD_INSTANCES can be
set to force it even in non-race test runs

Author: 3v1n0

Diff for: pam/integration-tests/helpers_test.go

@@ -81,7 +81,12 @@ func runAuthd(t *testing.T, gpasswdOutput, groupsFile string, currentUserAsRoot
 func sharedAuthd(t *testing.T) (socketPath string, gpasswdFile string) {
 	t.Helper()
 
-	if os.Getenv("AUTHD_TESTS_USE_INDIVIDUAL_AUTHD_INSTANCES") != "" {
+	sharedInstance := testutils.IsRace()
+	if s, err := strconv.ParseBool(os.Getenv("AUTHD_TESTS_USE_SHARED_AUTHD_INSTANCES")); err == nil {
+		sharedInstance = s
+	}
+
+	if !sharedInstance {
 		gPasswd := filepath.Join(t.TempDir(), "gpasswd.output")
 		groups := filepath.Join(testutils.TestFamilyPath(t), "gpasswd.group")
 		socket, cleanup, _ := runAuthdForTesting(t, gPasswd, groups, true)