LU-12661 tests: skip sanity 817 if kernel version >= 4.14

LU-12661 tests: skip sanity 817 if kernel version >= 4.14

sanity test_817 is in the ALWAYS_EXCEPT list for aarch64,
however it's failing because the test was done on kernel-alt
which is 4.14.x, it's not related with the architecture.

On new kernels nfsd is not releasing the file after write,
it will fail with ETXTBSY regardless of whether the nfs export
is backed by a lustre mount or not.

Skip the test on new kernels for now.

This patch is back-ported from the following one:
Lustre-commit: 4fed33473ca2964ff19f61fdb8501b2210f923de
Lustre-change: https://review.whamcloud.com/36712

Test-Parameters: trivial
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Change-Id: Ie18ceb961eee2313fca7d60a35159a7496075029
Reviewed-on: https://review.whamcloud.com/38259
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>