Could not start device session when devices are disconnected

Environment
Provide version numbers for the following components (information can be retrieved by running tns info in your project folder or by inspecting the package.json of the project):

• CLI: 6.1.0

Describe the bug
Your device is connected with USB and WiFi. If you disconnect it from Wifi and USB and make a change, you will see error:
Unable to apply changes for device: d97ff43f5d13677a2fb09fc9b4da3066464ff5f4. Error is: Could not start device session.

To Reproduce

1. tns create app --js
2. tns test init
3. tns test ios
4. disconnect device from USB nad WiFi and make a change. You will see exception.

Expected behavior
should continue to work

tns create app --js、tns test init、tns test ios で失敗を再現し、その後、変更を加える前にデバイスを USB と WiFi から切断します。報告された「Could not start device session」エラーの処理を追跡します。完了条件は、デバイスの切断後に変更を加えてもこの例外が発生しなくなることです。