path/filepath: remove code working around Join bug

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>

src/path/filepath/symlink.go

@@ -59,8 +59,7 @@ func walkLinks(path string, linksWalked *int) (string, error) {
 		return newpath, err
 	case file == "":
 		if isDriveLetter(dir) {
-			// appending "." to avoid bug in Join (see issue 11551)
-			return dir + ".", nil
+			return dir, nil
 		}
 		if os.IsPathSeparator(dir[len(dir)-1]) {
 			if isRoot(dir) {