Fix tap start/stop button not toggling at the right time (#1432)

Problem:
We depend on the websocketRequestSent bool (renamed to 
tapRequestInProgress in this branch) to determine whether the 
start/stop button says start or stop. However, we don't change 
this value in setState until we open the websocket connection 
(which could take some time). This led to a delay in when you 
press the Start button and when it changes colour.

Solution:
Set the state before waiting for the websocket to open, so the 
button colour changes immediately and the form feels more responsive

web/app/js/components/Tap.jsx

@@ -62,7 +62,7 @@ class Tap extends React.Component {
       },
       maxLinesToDisplay: 40,
       awaitingWebSocketConnection: false,
-      webSocketRequestSent: false,
+      tapRequestInProgress: false,
       showAdvancedForm: false,
       pollingInterval: 10000,
       pendingRequests: false
@@ -90,7 +90,6 @@ class Tap extends React.Component {
       ...query
     }));
     this.setState({
-      webSocketRequestSent: true,
       awaitingWebSocketConnection: false,
       error: ""
     });
@@ -101,13 +100,13 @@ class Tap extends React.Component {
   }
 
   onWebsocketClose = e => {
+    this.stopTapStreaming();
+
     if (!e.wasClean) {
       this.setState({
         error: `Websocket [${e.code}] ${e.reason}`
       });
     }
-
-    this.stopTapStreaming();
   }
 
   onWebsocketError = e => {
@@ -288,11 +287,11 @@ class Tap extends React.Component {
   startTapSteaming() {
     this.setState({
       awaitingWebSocketConnection: true,
+      tapRequestInProgress: true,
       tapResultsById: {},
       tapResultFilterOptions: this.getInitialTapFilterOptions()
     });
 
-
     let protocol = window.location.protocol === "https:" ? "wss" : "ws";
     let tapWebSocket = `${protocol}://${window.location.host}${this.props.pathPrefix}/api/tap`;
 
@@ -305,7 +304,7 @@ class Tap extends React.Component {
 
   stopTapStreaming() {
     this.setState({
-      webSocketRequestSent: false,
+      tapRequestInProgress: false,
       awaitingWebSocketConnection: false
     });
   }
@@ -442,7 +441,7 @@ class Tap extends React.Component {
           <Col span={colSpan}>
             <Form.Item>
               {
-                this.state.webSocketRequestSent ?
+                this.state.tapRequestInProgress ?
                   <Button type="primary" className="tap-stop" onClick={this.handleTapStop}>Stop</Button> :
                   <Button type="primary" className="tap-start" onClick={this.handleTapStart}>Start</Button>
               }