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.

Test-Parameters: ostcount=2 envdefinitions=SLOW=yes testlist=sanityn mdsfilesystemtype=zfs mdtfilesystemtype=zfs ostfilesystemtype=zfs
Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: I55b9267a3df68abc631b7d47886fb4b0f7e81594
Reviewed-on: http://review.whamcloud.com/8161
Reviewed-by: Bob Glossman <bob.glossman@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>