LU-4060 test: skip sanityn.sh test_74 on older than 2.4.93 MDS

LU-4060 test: skip sanityn.sh test_74 on older than 2.4.93 MDS

2.5 client 2.4 server interop testing shows that sanityn.sh test_74
needs to be skipped for Lustre MDS versions older than 2.4.93 .

Test-Parameters: testlist=sanityn clientdistro=el6 clientarch=x86_64 serverdistro=el6 serverarch=x86_64 serverjob=lustre-b2_4 serverbuildno=46
Signed-off-by: Emoly Liu <emoly.liu@intel.com>
Change-Id: I92d29a8db3ed5d145bd7db7bd18f5593ba80576c
Reviewed-on: http://review.whamcloud.com/7911
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>