Add unit tests for GetMCRegistryConf and IsDisconnectedOCP

Add comprehensive unit tests for the disconnected environment detection
and registry configuration retrieval functions in the util package.

Tests cover:
- IsNoMatchError: Detects both 'no matches for kind' (real API server) and
  'no kind is registered' (fake client) errors
- IsDisconnectedOCP: Tests with ICSP, IDMS, both, empty lists, and
  missing CRDs (graceful degradation)
- GetMCRegistryConf: Tests successful retrieval, missing MachineConfig,
  missing CRD, invalid ignition format, missing base64 prefix, and
  invalid base64 content
- Full scenario tests for disconnected environments and non-OpenShift
  cluster graceful degradation

The IsNoMatchError function is updated to also detect 'no kind is registered'
errors which occur in functional tests where the fake client behaves
differently than a real Kubernetes API server.

The MachineConfigNotFound test verifies that IsNotFound errors are NOT
treated as IsNoMatchError - when the CRD exists but the resource doesn't,
this should be an error (not a warning), indicating misconfiguration.

Author: stuggi

internal/dataplane/util/image_registry.go

@@ -81,8 +81,13 @@ func IsDisconnectedOCP(ctx context.Context, helper *helper.Helper) (bool, error)
 
 // IsNoMatchError checks if the error indicates that a CRD/resource type doesn't exist
 func IsNoMatchError(err error) bool {
-	// Check for "no matches for kind" type errors which indicate the CRD doesn't exist
-	return strings.Contains(err.Error(), "no matches for kind")
+	errStr := err.Error()
+	// Check for "no matches for kind" type errors which indicate the CRD doesn't exist.
+	// Also check for "no kind is registered" which occurs when the type isn't in the scheme.
+	// This is specifically needed for functional tests where the fake client returns a different
+	// error type than a real Kubernetes API server when CRDs are not installed.
+	return strings.Contains(errStr, "no matches for kind") ||
+		strings.Contains(errStr, "no kind is registered")
 }
 
 // GetMCRegistryConf - will unmarshal the MachineConfig ignition file the machineConfigIgnition object.