add check before removing mjpegServerPortCapability (#505)

Author: sudharsan-selvaraj

src/CapabilityManager.ts

@@ -44,16 +44,15 @@ export async function iOSCapabilities(
   if (!isCapabilityAlreadyPresent(caps, 'appium:mjpegServerPort')) {
     if (freeDevice.realDevice) {
       caps.firstMatch[0]['appium:mjpegServerPort'] = await getPort();
-      delete caps.alwaysMatch['appium:mjpegServerPort'];
     } else {
       /* In simulator, port forwarding won't happen for each session. So mjpegServerPort will be used only for 1st time.
        * So set the port for the first time and resuse the same port for subsequent sessions.
        */
       const existingPort = freeDevice.mjpegServerPort;
       caps.firstMatch[0]['appium:mjpegServerPort'] =
         existingPort && (await isPortBusy(existingPort)) ? existingPort : await getPort();
-      delete caps.alwaysMatch['appium:mjpegServerPort'];
     }
+    deleteAlwaysMatch(caps, 'appium:mjpegServerPort');
     deleteAlwaysMatch(caps, 'appium:udid');
     deleteAlwaysMatch(caps, 'appium:deviceName');
     deleteAlwaysMatch(caps, 'appium:wdaLocalPort');