- revert broken hunk in vserver patch

After the following change that went into 3.13.9 and 3.14+, vserver
enabled kernels couldn't boot anymore, hanging at the first interaction
with udev in initrd. Reverting the change to follow_dotdot() in
fs/namei.c makes the kernel boot again without problems.

 From b37199e626b31e1175fb06764c5d1d687723aac2 Mon Sep 17 00:00:00 2001
 From: Al Viro <viro@zeniv.linux.org.uk>
 Date: Thu, 20 Mar 2014 15:18:22 -0400
 Subject: rcuwalk: recheck mount_lock after mountpoint crossing attempts