LU-15065 quota: fix BIO write performance drop

LU-15065 quota: fix BIO write performance drop

Before the patch qti_lqes_qunit_min used int to store qunit
value, while lqe_qunit type is _u64. lqe_qunit > 2G caused
an overflow in a local integer argument. For example, when
block hard limit was set to 500TB(i.e. lqe_qunit was about
64TB in a system with 2 OSTs), qti_lqes_qunit_min returned
0 instead of 64TB in a qmt_lvbo_fill. Thus new qunit was not
set on OSTs(qsd_set_qunit wasn't called). Without the qunit,
OST began to send release request after each acquire. For
example, to write 10MB at the OST were sent 2 acquire and
2 release reuests(as qunit was not set on OST). With the
fix, i.e. in a normal case, OST needs just one acquire
request. The issue caused performance drop in a bufferred
write up to 15%-20% if compare with a baseline without PQ
patches.

Note, the issue exists only when a hard limit is set to some
high value(>100GB). The exact hard limit value depends on OSTs
number in a system and on amount of used space, but let's think
that issue doesn't exist on a clean system with 2 OSTs and hard
block limit 100G(this case was checked).

Remove qmt_pool_hash - it is not used anywhere since
"LU-11023 quota: remove quota pool ID".

HPE-bug-id: LUS-10250
Change-Id: I2c4ce38f5b9395ed1f4868d4c8efc00751116b15
Signed-off-by: Sergey Cheremencev <sergey.cheremencev@hpe.com>
Reviewed-on: https://review.whamcloud.com/45133
Reviewed-by: Petros Koutoupis <petros.koutoupis@hpe.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>