Subscription initialization throws "Invalid message type string" exception when token has expired

**Describe the bug**
The issue happens when app tries to initialize subscription with an expired token.
`WebSocketConnectionManager.processJsonMessag(websocket, message)` gets as message:

`{"type":"connection_error","payload":{"errors":[{"errorType":"Unauthorized","errorCode":401}]}}`

which cannot be parsed because **connection_error** does not exists in MessageType enum.
So the result is `IllegalArgumentException("Invalid message type string");`

**To Reproduce**
Steps to reproduce the behavior:
Provide expired token during subscription initialization.

**Expected behavior**
New MessageType suitable to code 401 should be added so `IllegalArgumentException("Invalid message type string");` won't be thrown. And subscription request should be repeated with the refreshed token.

**Environment(please complete the following information):**
- AppSync SDK Version: 3.0.1

**Device Information (please complete the following information):**
- Samsung Galaxy S7 edge
- Android Version: 8.0.0

Start at WebSocketConnectionManager.processJsonMessag(websocket, message) and inspect the MessageType enum to trace handling of the connection_error payload. Reproduce subscription initialization with an expired token; done means the 401 response no longer causes IllegalArgumentException and the subscription request is retried with the refreshed token.

Written by the indexing model from the issue text.