LU-7846 mdt: mount with fileset info from nodemap

LU-7846 mdt: mount with fileset info from nodemap

Enforce subdir mount if client is in a nodemap for
which fileset information is set.

Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: Ibf1077389dac66fce7c2e88ab64573619545119b
Reviewed-on: http://review.whamcloud.com/18784
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Wang Shilong <wshilong@ddn.com>
Reviewed-by: Li Xi <lixi@ddn.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>