LU-4181 tests: disable lnet_selftest.sh for DNE.

Disable lnet_selftest for DNE to make review pass with DNE.

Signed-off-by: wang di <di.wang@intel.com>
Change-Id: Ie4abd794d0184955af84752f0a9c64181b85f1ec
Reviewed-on: http://review.whamcloud.com/8130
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Tested-by: Jenkins
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>