Move the test skip to use testenv.SkipFlaky and link to the Go issue.

Update #24826

Change-Id: I7a0ea3325ffcaa790b25f8cdc429fb52e96a41c7
Reviewed-on: https://go-review.googlesource.com/106636Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>