LU-4647 tests: modify sanity-sec to test multiple MDSes

LU-4647 tests: modify sanity-sec to test multiple MDSes

This patch modifies santiy-sec to distribute the nodemap to all the
MDSes in the system. It also uses test_mkdir to create directories on
multiple MDTs, allowing DNE and nodemapping to be tested.

Test-Parameters: alwaysuploadlogs envdefinitions=SLOW=yes \
mdtfilesystemtype=ldiskfs mdsfilesystemtype=ldiskfs ostfilesystemtype=ldiskfs \
mdtcount=4 testlist=sanity-sec

Signed-off-by: Kit Westneat <kit.westneat@gmail.com>
Change-Id: I48f47b72e404614167c715a682d99351295d8189
Reviewed-on: http://review.whamcloud.com/13343
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Jian Yu <jian.yu@intel.com>
Reviewed-by: Nathaniel Clark <nathaniel.l.clark@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>