LU-2882 build: build broken with no zfs libraries installed

LU-2882 build: build broken with no zfs libraries installed

Reverting default values (originaly set in LU-2391 patch) for
ldiskfs/zfs OSD RPMs builds, to comply for more ways
("rpmbuild -tb <lustre_source_tarball>") used to build Lustre.

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Change-Id: I07eca22d03f597942284bbbc0bfd1b680ecb199b
Reviewed-on: http://review.whamcloud.com/5661
Tested-by: Hudson
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Alexey Lyashkov <alexey_lyashkov@xyratex.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>