[release-branch.go1.8] net: increase expected time to dial a closed port on all Darwi...

[release-branch.go1.8] net: increase expected time to dial a closed port on all Darwin ports

All current darwin architectures seem to take at least 100ms to dial a closed port,
and that was making the all.bash script fail.

Fixes #22062

Change-Id: Ib79c4b7a5db2373c95ce5d993cdcbee55cc0667f
Reviewed-on: https://go-review.googlesource.com/67350
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-on: https://go-review.googlesource.com/71331
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>