Increase the key size for KubeConfig private key

It's now required to have a minimum of 1024 bits the RSA private key.
https://pkg.go.dev/crypto/rsa@master#GenerateKey

Signed-off-by: Arnaud Meukam <[email protected]>

Author: ameukam

pkg/kubeconfig/create_kubecfg_test.go

@@ -142,7 +142,7 @@ func fakeKeyset() *fi.Keyset {
 
 func TestBuildKubecfg(t *testing.T) {
 	originalPKIDefaultPrivateKeySize := pki.DefaultPrivateKeySize
-	pki.DefaultPrivateKeySize = 512
+	pki.DefaultPrivateKeySize = 2048
 	defer func() {
 		pki.DefaultPrivateKeySize = originalPKIDefaultPrivateKeySize
 	}()