Check for Nil response (PHNX-3021) (#2)

Motivation
---
Without checking for a nil value for the response from a client.Do call, we run the risk of attempting to reference a property of a null object which would cause our program to hard crash.

This is based off my own learning of Go and the following reference:
https://medium.com/@KeithAlpichi/go-gotcha-closing-a-nil-http-response-body-with-defer-9b7a3eb30e8c

I may be off base; in which case, we can ignore this PR.

Modification
---
- Check the response from our client call and return err if the resp is null

https://centeredge.atlassian.net/browse/PHNX-3021

notifier.go

@@ -46,16 +46,19 @@ func notifyStateChange(info *monitorInfo, newStatus bool) error {
 	for i := 0; i < retryAttempts; i++ {
 		client := &http.Client{}
 		resp, err := client.Do(req)
-		defer resp.Body.Close()
+		if resp != nil {
 
-		log.WithFields(log.Fields{
-			"svc": info.ServiceName,
-			"pod": info.PodName,
-			"ns":  info.Namespace,
-		}).Debug("Notification result ", resp.Status)
+			defer resp.Body.Close()
 
-		if err == nil {
-			return nil
+			log.WithFields(log.Fields{
+				"svc": info.ServiceName,
+				"pod": info.PodName,
+				"ns":  info.Namespace,
+			}).Debug("Notification result ", resp.Status)
+
+			if err == nil {
+				return nil
+			}
 		}
 
 		time.Sleep(retryInterval)