Fix #1009: diabling metrics caused a NRE in TransportRequestState

Author: gmarz

src/Elasticsearch.Net/Connection/RequestState/TransportRequestState.cs

@@ -94,7 +94,7 @@ public TransportRequestState(
 			this.RequestParameters = requestParameters;
 			this._traceEnabled = settings.TraceEnabled;
 			this._metricsEnabled = settings.MetricsEnabled;
-			if (this._metricsEnabled)
+			if (this._metricsEnabled || this._traceEnabled)
 				this._stopwatch = Stopwatch.StartNew(); 
 
 			this.Method = method;