[cmd/opampsupervisor] Fix leaks in e2e tests (#32477)

**Description:** Fix leaks in e2e tests

**Link to tracking Issue:** resolve #30931

cmd/opampsupervisor/e2e_test.go

@@ -513,6 +513,7 @@ func TestSupervisorOpAMPConnectionSettings(t *testing.T) {
 			},
 		},
 	})
+	waitForSupervisorConnection(newServer.supervisorConnected, true)
 
 	require.Eventually(t, func() bool {
 		return connectedToNewServer.Load() == true

cmd/opampsupervisor/package_test.go

@@ -0,0 +1,14 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package main
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m)
+}