Re-add error for loading HCP management token

agent/hcp/bootstrap/bootstrap.go

@@ -457,7 +457,7 @@ func loadManagementToken(dir string) (string, error) {
 	bytes, err := os.ReadFile(name)
 	if os.IsNotExist(err) {
 		// A missing management token is not an error, if none was provided by HCP
-		return "", nil
+		return "", errors.New("configuration files on disk are incomplete, missing: " + name)
 	}
 	if err != nil {
 		return "", fmt.Errorf("failed to read: %w", err)

agent/hcp/bootstrap/bootstrap_test.go

@@ -372,7 +372,7 @@ func Test_loadPersistedBootstrapConfig(t *testing.T) {
 			existingCluster:        true,
 			disableManagementToken: true,
 			expect: expect{
-				loaded: true,
+				loaded: false,
 			},
 		},
 		"existing cluster no files": {
@@ -398,7 +398,7 @@ func Test_loadPersistedBootstrapConfig(t *testing.T) {
 		"new cluster with no token": {
 			disableManagementToken: true,
 			expect: expect{
-				loaded: true,
+				loaded: false,
 			},
 		},
 		"new cluster some files": {