Windows has a low resolution timer.
Some of the tests assumed that unblock takes effect immediately.
Consider:
t := time.Now()
elapsed := time.Now().After(t)
It seems plausible that elapsed should always be true.
However, with a low resolution timer, that might fail.
Change time.Now().After to !time.Now().Before,
so that unblocking always takes effect immediately.
Fixes#873.
This is a lot like wiring up a local UDP socket, read and write
deadlines work. The big difference is the Block feature, which
lets you stop the packet flow without breaking the connection.
This lets you emulate broken sockets and test timeouts actually
work.
Signed-off-by: David Crawshaw <crawshaw@tailscale.com>
