If ->follow_link handler return the error, it should decrement
nd->path refcnt. But, ecryptfs_follow_link() doesn't decrement.

This patch fix it by using usual nd_set_link() style error handling,
instead of playing with nd->path.
Signed-off-by: NOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>