LU-13639 tests: increase limit in sanity-quota t_2

LU-13639 tests: increase limit in sanity-quota t_2

If limit is equal to the least_qunit, slave target may
preacquire more quota while creating "limit number" of files
causing EDQUOT. Change limit from soft_qunit to 2 soft_qunit.
The patch also changes test behaviour - createmany is devided
to 2 parts. Firstly, it creates (limit-least_qunit) nodes and
check that there is no EDQUOT. Then it creates least_qunit
nodes and ignore the result of creating - it is a valid case
if it hits the limit. And only after that check that we
can't create nodes over quota.

Change-Id: Iad7c1cc05119c8d3e0f1cfc2adffb276d79f18c7
Test-Parameters: testgroup=review-dne-zfs-part-4
Test-Parameters: testlist=sanity-quota env=ONLY=2, ONLY_REPEAT=200
Signed-off-by: Sergey Cheremencev <sergey.cheremencev@hpe.com>
Reviewed-on: https://review.whamcloud.com/45943
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Andrew Perepechko <andrew.perepechko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>