os: eliminate arbitrary timeout in testClosewithBlockingRead

os: eliminate arbitrary timeout in testClosewithBlockingRead

The 1-second timeout on execution of this test is empirically too
short on some platforms. Rather than trying to tune the timeout, allow
the test to time out on its own (and dump goroutines) if it deadlocks.

Fixes #57993.
Fixes #57994.

Change-Id: I69ee86c75034469e4b4cd391b8dc5616b93468b8
Reviewed-on: https://go-review.googlesource.com/c/go/+/463180
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Bryan Mills <bcmills@google.com>