Revert "LU-3627 quota: Fix incorrect NULL return value of qsd_init()"

This reverts commit 7c93d397d18f5f5380a969f52a806c28b2c78d54

Change-Id: I87d20ff338775a5cfdbc22cc7243ffdb5b0957eb
Reviewed-on: http://review.whamcloud.com/7197
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Tested-by: Oleg Drokin <oleg.drokin@intel.com>