LU-6247 tests: fix nodemap quota test to use correct blocksize

LU-6247 tests: fix nodemap quota test to use correct blocksize

The nodemap quota test needs to take into account indirect blocks and
other overhead when deciding if the quota used is excessive. It's
supposed to add the fs blocksize * 2, so 8k on ldiskfs and 256k on
zfs, but it was using the osc block size instead of the osd
blocksize. This patch modifies the test to use the fs_log_size helper
to determine an appropriate fuzz size.

Test-Parameters: mdtfilesystemtype=zfs mdsfilesystemtype=zfs ostfilesystemtype=zfs testlist=sanity-sec
Signed-off-by: Kit Westneat <kit.westneat@gmail.com>
Change-Id: I3bf6380fd0a0e6b3246343da8a139c6b4ea120ae
Reviewed-on: http://review.whamcloud.com/13844
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Reviewed-by: Isaac Huang <he.huang@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>