Updates MachineSet tests to use GenerateName

Use GenerateName when creating MachineSet instances to avoid test
flakes.

Turs out the DeleteAll call in the cleanup function is async, so
occasionally we were seeing test failures where the instance name was being
reused, but the previous instance had not deleted yet.

pkg/controller/machineset/machineset_controller_test.go

@@ -91,7 +91,7 @@ var _ = Describe("MachineSet Reconciler", func() {
 		By("Setting up the machine set builder")
 		machineSetBuilder = machinev1resourcebuilder.MachineSet().
 			WithNamespace(namespace.ObjectMeta.Name).
-			WithName("foo").
+			WithGenerateName("foo").
 			WithReplicas(replicas).
 			WithLabels(map[string]string{"foo": "bar"})
 
@@ -151,7 +151,7 @@ var _ = Describe("MachineSet Reconciler", func() {
 
 	It("Should set the Paused condition appropriately", func() {
 		instance := machineSetBuilder.
-			WithName("baz").
+			WithGenerateName("baz").
 			WithLabels(map[string]string{"baz": "bar"}).
 			Build()