LU-8730 test: Remove duplicate $dev from conf-sanity test_83

LU-8730 test: Remove duplicate $dev from conf-sanity test_83

Remove duplicate $dev variable passed to add function, which
passes it as argument to mkfs.lustre. mkfs.lustre utility in
Lustre 2.1 throws error when multiple device names passed to it.
Skip test if OSTs are not ldiskfs-based.

Test-Parameters: trivial envdefinitions=ONLY=83 testlist=conf-sanity
Change-Id: I56535aac27e25bbf359bda835b24a56a4101c8ed
Seagate-bug-id: MRP-2239
Signed-off-by: Ashish Maurya <ashish.maurya@seagate.com>
Signed-off-by: Sushant Mane <sushant.mane@seagate.com>
Reviewed-on: http://es-gerrit.xyus.xyratex.com:8080/9425
Tested-by: Jenkins
Reviewed-by: Sergey Cheremencev <sergey.cheremencev@seagate.com>
Reviewed-by: Ujjwal Lanjewar <ujjwal.lanjewar@seagate.com>
Tested-by: Elena V. Gryaznova <elena.gryaznova@seagate.com>
Signed-off-by: Ashish Maurya <ashish.maurya@seagate.com>
Reviewed-on: https://review.whamcloud.com/23249
Reviewed-by: Jian Yu <jian.yu@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>