Use defer style to stop tickers to avoid current/possible misuse (#5883)

This commit ensures that all tickers are stopped using defer ticker.Stop()
style. This will also fix one bug seen when a client starts to listen to
event notifications and that case will result a leak in tickers.

cmd/admin-handlers.go

@@ -500,6 +500,7 @@ func (a adminAPIHandlers) HealHandler(w http.ResponseWriter, r *http.Request) {
 	// after 10s unless a response item comes in
 	keepConnLive := func(w http.ResponseWriter, respCh chan healResp) {
 		ticker := time.NewTicker(time.Second * 10)
+		defer ticker.Stop()
 		started := false
 	forLoop:
 		for {
@@ -528,7 +529,6 @@ func (a adminAPIHandlers) HealHandler(w http.ResponseWriter, r *http.Request) {
 				break forLoop
 			}
 		}
-		ticker.Stop()
 	}
 
 	// find number of disks in the setup