LU-10712 tests: skip conf-sanity 108[a,b] for old server

LU-10712 tests: skip conf-sanity 108[a,b] for old server

Patch skips test_108a and test_108b for old servers.

Signed-off-by: Elena Gryaznova <c17455@cray.com>
Cray-bug-id: LUS-5691
Test-Parameters: trivial testlist=conf-sanity
Change-Id: I7494e15710ac2663a0e01a9d3568fa5bcd590a6a
Reviewed-on: https://review.whamcloud.com/31413
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Vladimir Saveliev <c17830@cray.com>
Reviewed-by: Vitaly Fertman <c17818@cray.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>