Device selection now always shows the device that it managed to open. (#4384)

* Device selection now always shows the device that managed to open.

* Simplifies implementation, skips using state.

react/features/device-selection/components/DeviceSelection.js

                 label: 'settings.selectCamera',
                 onSelect: selectedVideoInputId =>
                     super._onChange({ selectedVideoInputId }),
-                selectedDeviceId: this.props.selectedVideoInputId
+                selectedDeviceId: this.state.previewVideoTrack
+                    ? this.state.previewVideoTrack.getDeviceId() : null
             },
             {
                 devices: availableDevices.audioInput,
                 label: 'settings.selectMic',
                 onSelect: selectedAudioInputId =>
                     super._onChange({ selectedAudioInputId }),
-                selectedDeviceId: this.props.selectedAudioInputId
+                selectedDeviceId: this.state.previewAudioTrack
+                    ? this.state.previewAudioTrack.getDeviceId() : null
             }
         ];