net: prevent spurious TCP connection setup notification on darwin
On the latest darwin kernels, kevent in runtime-integrated network
poller sometimes reports SYN-SENT state sockets as ESTABLISHED ones,
though it's still unclear what's the root cause.
This change prevents such spurious notifications by additional connect
system calls.
Fixes #14548.
Change-Id: Ie29788e38ca735ca77259befeba3229d6a30ac52
Reviewed-on: https://go-review.googlesource.com/20468
Run-TryBot: Mikio Hara <mikioh.mikioh@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>