EvalSymlinks code assumes that Join has a bug
(see issue #11551 for details). But issue #11551 has
been fixed. Remove the workaround so it does not
confuses us when we read code next time.

Change-Id: I06bea20189f01f9922237c05516847353d8e4736
Reviewed-on: https://go-review.googlesource.com/17620Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>