Properly time mephisto-task out on "Initializing...."

[JackUrb]

There are many reports of workers connecting to a task only to be stuck on "Initializing" forever. This occurs when the Mephisto routing server is set up, but the backend is not connected.

We should provide better error messaging to the workers when this occurs, and ideally get a message to the task owner as it indicates improper shutdown or a connectivity issue.

[pringshia]

Some more context:

On the initial handshake, when getting agentId, the handshake goes to the router, but doesn't reach the router, we hang forever for a response.

Two error cases:

• Router is aware that the server is down (no hearbeat after X mins), all subsequent messages result in 500x-esque error
• If there actually was a timeout issue but the server and router are still up (either the front-end sends another request or user refreshes)

To repro:

• Start up a server, kill Mephisto with a pipe (Ctrl+) and not with a Ctrl+C (this skips all the shutdown processes but the router is still running)