LU-5436 quota: use OBD_SLAB_FREE_PTR() to free lqe

lquota entries are allocated with OBD_SLAB_ALLOC_PTR() and should be
freed with OBD_SLAB_FREE_PTR() instead of OBD_FREE_PTR().
This issue has no real side effect since the Linux VM picks up the
correct slab.
This patch also fixes some incorrect error messages.

Signed-off-by: Johann Lombardi <johann.lombardi@intel.com>
Change-Id: I07effa69ae877537b5339fe1c20fabce44468822
Reviewed-on: http://review.whamcloud.com/11289
Tested-by: Jenkins
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>