net: don't wait 5 seconds to re-read /etc/resolv.conf
If a Go process starts up, finds /etc/resolv.conf empty, then the DHCP
client writes /etc/resolv.conf, the Go program would find itself
broken for up to 5 seconds.
We noticed this during integration tests in ephemeral VMs using
gokrazy that boot into our application.
Change-Id: Ia64c2b5c698a4ee3efc15d8a8f1850c47e531b84
Reviewed-on: https://go-review.googlesource.com/c/go/+/739620 Reviewed-by: Damien Neil <dneil@google.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>