fix lint warnings in pilot (istio#1817)

Automatic merge from submit-queue.

fix lint warnings in pilot

I see the following lint warnings in pilot. This PR fixes those
trivial lint warnings.

```
pilot/cmd/pilot-discovery/main.go:176::warning: declaration of "client" shadows declaration at pilot/cmd/pilot-discovery/main.go:103 (vetshadow)
pilot/platform/kube/conversion_test.go:208:13:warning: if block ends with a return statement, so drop this else and outdent its block (golint)
```

**What this PR does / why we need it**:

**Which issue this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close that issue when PR gets merged)*: fixes #

**Special notes for your reviewer**:

**Release note**:

```release-note
none
```

pilot/cmd/pilot-discovery/main.go

@@ -173,13 +173,13 @@ var (
 						})
 				case platform.EurekaRegistry:
 					glog.V(2).Infof("Eureka url: %v", flags.eureka.serverURL)
-					client := eureka.NewClient(flags.eureka.serverURL)
+					eurekaClient := eureka.NewClient(flags.eureka.serverURL)
 					serviceControllers.AddRegistry(
 						aggregate.Registry{
 							Name: serviceRegistry,
 							// TODO: Remove sync time hardcoding!
-							Controller:       eureka.NewController(client, 2*time.Second),
-							ServiceDiscovery: eureka.NewServiceDiscovery(client),
+							Controller:       eureka.NewController(eurekaClient, 2*time.Second),
+							ServiceDiscovery: eureka.NewServiceDiscovery(eurekaClient),
 							ServiceAccounts:  eureka.NewServiceAccounts(),
 						})
 				default:

pilot/platform/kube/conversion_test.go

@@ -205,9 +205,8 @@ func TestServiceSecurityAnnotation(t *testing.T) {
 				Annotations: func() map[string]string {
 					if test.port > 0 {
 						return map[string]string{portAuthenticationAnnotationKey(test.port): test.annotationValue}
-					} else {
-						return nil
 					}
+					return nil
 				}(),
 			},
 			Spec: v1.ServiceSpec{