Simplify access to local node name (#11907)

The local node name is heavily used in tracing, create a new global 
variable to store it. Multiple goroutines can access it since it won't be
changed later.

cmd/admin-handlers.go

@@ -517,7 +517,7 @@ func (a adminAPIHandlers) StartProfilingHandler(w http.ResponseWriter, r *http.R
 
 	vars := mux.Vars(r)
 	profiles := strings.Split(vars["profilerType"], ",")
-	thisAddr, err := xnet.ParseHost(GetLocalPeer(globalEndpoints))
+	thisAddr, err := xnet.ParseHost(globalLocalNodeName)
 	if err != nil {
 		writeErrorResponseJSON(ctx, w, toAdminAPIErr(ctx, err), r.URL)
 		return