LU-2469 tests: use MDS/OSTDEV and MDS/OSTDEVBASE with zfs

LU-2469 tests: use MDS/OSTDEV and MDS/OSTDEVBASE with zfs

Add support for using MDSDEVn, OSTDEVn, MDSDEVBASE and OSTDEVBASE
variables when testing with zfs.
Add *ZFSDEVn variable for specifying ZFS format devices.
Remove use of *DEVn use outside of test-framework.sh

MDSDEV et al. specify physical device formatted.

Formerly Change-Id I89115ce935294cdbbd6620fec3f9dc3eb76f8960

Test-Parameters: mdsfilesystemtype=zfs ostfilesystemtype=zfs  mdtfilesystemtype=zfs testlist=sanity
Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: If6506995d9d61f9c97827f45071f0d317c7a09f9
Reviewed-on: http://review.whamcloud.com/5016
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Li Wei <wei.g.li@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>