LU-2831 tests: Sync MDS data also when doing sync_all_data

LU-2831 tests: Sync MDS data also when doing sync_all_data

The quota data was differing in sanity-quota/35 before and after
restart because the MDS data had not synced prior to checking the
values.  This patch forces MDS data to sync whenever sync_all_data is
called.  This should prevent this error from recurring here and
elsewhere.

Signed-off-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Change-Id: Ic2e1dafefbc2d83fc281d76845504c4547dd0694
Reviewed-on: http://review.whamcloud.com/6142
Tested-by: Hudson
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Niu Yawei <yawei.niu@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>