EX-3342 tests: fix Lustre version in skip checks in conf-sanity

EX-3342 tests: fix Lustre version in skip checks in conf-sanity

Many patches land to the EXAScaler branches as ports from
other branches.  Sometimes the tests that are included with
the ported patches check the version of Lustre to ensure
that the feature it tests exists in this version of Lustre.
These version values are not always changed when patches
are ported from one branch to another.

Change Lustre test suite version checks to be relative to
this branch. Conf-sanity test_126 was modified.

Fixes: efd1b764bac ("LU-11814 obd: Crashed while mount in parallel")

Test-Parameters: env=ONLY="126" serverversion=2.10.8 serverdistro=el7.6 \
testlist=conf-sanity
Test-Parameters: env=ONLY="126" clientversion=2.12.6-ddn42 testlist=conf-sanity
Test-Parameters: env=ONLY="126" serverversion=2.12.6-ddn42 testlist=conf-sanity
Test-Parameters: trivial env=ONLY="126" testlist=conf-sanity

Lustre-change: https://review.whamcloud.com/45942/
Lustre-commit: 5f2b47b4d9fb4625290c9fa498c776b3df15ceb9

Signed-off-by: Alena Nikitenko <anikitenko@ddn.com>
Change-Id: I953be8ec00e28b09eb492ffa24c03c50430f59df
Reviewed-on: https://review.whamcloud.com/46365
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>