LU-4719 mdt: Don't try to print non-existent objects

LU-4719 mdt: Don't try to print non-existent objects

mdt_dump_lmm() needs to make sure it's not trying to print
objects for a default striping from a directory, since there
are not objects in this case.

Return early if the D_INFO debug mask is disenabled, so it
doesn't iterate through the LOV/LMV layout at all.  That is
just a waste of effort.

Lustre-change: http://review.whamcloud.com/#/c/9520
Lustre-commit: ebfc6f4b54961e5e0762af7d2555f2dc5d1e1ec3

Signed-off-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Nunez <james.a.nunez@intel.com>
Change-Id: Ifbda7c0bfdec74c5ee4c097ea24613a4ce692572
Reviewed-on: http://review.whamcloud.com/10021
Tested-by: Jenkins
Reviewed-by: James Simmons <uja.ornl@gmail.com>
Reviewed-by: Matt Ezell <ezellma@ornl.gov>
Tested-by: Maloo <hpdd-maloo@intel.com>