[release-branch.go1.9] godoc: don't try to follow all symlinks

Revert https://golang.org/cl/45096.

Original change description:
    godoc: follow symbolic links to folders in GOROOT

    Directory walking in godoc relies on ReadDir which returns the result
    of os.Lstat.

    Instead make the the OS VFS's ReadDir use os.Stat on symlinks before

Updates golang/go#15049
Fixes golang/go#21061

Change-Id: Ieaa7923d85842f3da5696a7f46134d16407dae66
Reviewed-on: https://go-review.googlesource.com/53634
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-on: https://go-review.googlesource.com/57870
Reviewed-by: Russ Cox <rsc@golang.org>
2 files changed