Use short test to signal that we dont run integration

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

integration_embedded_derp_test.go

@@ -45,6 +45,10 @@ type IntegrationDERPTestSuite struct {
 }
 
 func TestIntegrationDERPTestSuite(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping integration tests due to short flag")
+	}
+
 	saveLogs, err := GetEnvBool("HEADSCALE_INTEGRATION_SAVE_LOG")
 	if err != nil {
 		saveLogs = false