obey timeout in CommandConnectSimple.get_handshake
obey timeout in CommandConnectSimple.get_handshake

Summary:
if the server is hosed and not responding to its socket, then clients trying to handshake with it currently can block forever.

there's a long-standing TODO about making `Marshal_tools` use `Timeout`. it does!

passing the timeout works in my test on Windows.

before:
```
PS> flow stop
Trying to connect to server for `C:\...\test`
# hangs indefinitely
```

after:
```
PS> flow stop
Trying to connect to server for `C:\...\test`
Attempting to meanly kill server for `C:\...\test`
Successfully killed server for `C:\...\test`
PS>
```

Reviewed By: samwgoldman

Differential Revision: D35412721

fbshipit-source-id: f66c0c093e040775f8f6fcdfe613e1caa4cfd043

facebook/flow,mroch/flow,mroch/flow,mroch/flow,facebook/flow,mroch/flow,facebook/flow,mroch/flow,mroch/flow,facebook/flow,facebook/flow,mroch/flow,facebook/flow,facebook/flow