Check whether static cert is already configured in UpdateTransportConfig

- Also update test-cmd.sh to pass a signing ca to the kube controller
  manager, so CSRs work properly in integration tests.

Signed-off-by: Margo Crawford <margaretc@vmware.com>

Kubernetes-commit: f015fd66ce95d02cd66efc263eb9e5441b42a17d

plugin/pkg/client/auth/exec/exec_test.go

@@ -1206,6 +1206,13 @@ func TestAuthorizationHeaderPresentCancelsExecAction(t *testing.T) {
 				config.Password = "zelda"
 			},
 		},
+		{
+			name: "cert auth",
+			setTransportConfig: func(config *transport.Config) {
+				config.TLS.CertData = []byte("some-cert-data")
+				config.TLS.KeyData = []byte("some-key-data")
+			},
+		},
 	}
 	for _, test := range tests {
 		t.Run(test.name, func(t *testing.T) {