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.

Test-Parameters: trivial
Signed-off-by: Li Dongyang <dongyangli@ddn.com>
Change-Id: Ie18ceb961eee2313fca7d60a35159a7496075029
Reviewed-on: https://review.whamcloud.com/36712
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: James Nunez <jnunez@whamcloud.com>