Sliver client unresponsive after portfwd connection failure

[pooki3bear]

Describe the bug sliver client becomes unresponsive while waiting on network read when using the portforward feature.

To Reproduce Steps to reproduce the behavior:

1. Configure portforward is configured to an unstable, or non-existent destination
2. Send packets

Expected behavior Expect sliver client session to still operate under sub-optimal portfwd network conditions

Desktop (please complete the following information):

• OS: MacOS
• Version v1.4.17, v1.14.20 clients

Additional context Add any other context about the problem here.

[rkervella]

It's probably due to a timeout on the first forwarded TCP connection, we could probably set a lower timeout than the gRPC default timeout.