Remove race condition in templated test code "StartTestManager" function.

[shaneutt]

Hello! When working with kubebuilder it was noticed that the templated testing code provided for a new project technically has a race condition in it, specifically it appears to be the StartTestManager function in pkg/scaffold/controller/controllersuitetest.go.

Here's a diff of my suggestion for a fix for this:

diff --git a/pkg/scaffold/controller/controllersuitetest.go b/pkg/scaffold/controller/controllersuitetest.go
index bbdfff7c..37001ca2 100644
--- a/pkg/scaffold/controller/controllersuitetest.go
+++ b/pkg/scaffold/controller/controllersuitetest.go
@@ -96,10 +96,10 @@ func SetupTestReconcile(inner reconcile.Reconciler) (reconcile.Reconciler, chan
 func StartTestManager(mgr manager.Manager, g *gomega.GomegaWithT) (chan struct{}, *sync.WaitGroup) {
        stop := make(chan struct{})
        wg := &sync.WaitGroup{}
+       wg.Add(1)
        go func() {
-               wg.Add(1)
+               defer wg.Done()
                g.Expect(mgr.Start(stop)).NotTo(gomega.HaveOccurred())
-               wg.Done()
        }()
        return stop, wg
 }

Here is a PR for this: #572

Thank you! 👍