LU-2829 tests: Decrease load on zfs for sanityn/33a-b

LU-2829 tests: Decrease load on zfs for sanityn/33a-b

Decrease number of files when testing sanityn/33a and 33b when using
ZFS due to performance issues (cf LU-2887).  ZFS performance when
commit_on_sharing is enabled is very slow.

Lustre-commit: 4add39c3775a69c2b3daf212b8e3fc9976bd53e6
Lustre-change: http://review.whamcloud.com/8161

Test-Parameters: ostcount=2 envdefinitions=SLOW=yes testlist=sanityn mdsfilesystemtype=zfs mdtfilesystemtype=zfs ostfilesystemtype=zfs

Signed-off-by: Bob Glossman <bob.glossman@intel.com>
Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Change-Id: I79b6b6c315b7f349120301db514aaf84b7dfb94f
Reviewed-on: http://review.whamcloud.com/8273
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>