LU-1812 ldiskfs: don't use sb->s_qf_inums

LU-1812 ldiskfs: don't use sb->s_qf_inums

ext4-quota-first-class.patch was finally accepted into the mainline
Linux kernel via commit 7c319d32 (v3.6). The final version doesn't
include the cached inode numbers so they aren't available on newer
kernels that include this patch (or that are using an ldiskfs
patched using the usptream version).

Since the file system will refuse mounting when the inodes can't
be read, the lookup code isn't invoked without valid inode numbers
anyway.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Change-Id: Ie1b824183cf734a0f242bb6483a192f1919dc4be
Reviewed-on: http://review.whamcloud.com/5264
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Johann Lombardi <johann.lombardi@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>