staging/lustre/lmv: fix duplicate directory entries

In 4e57f6dd3a156e35ccb587fc5c003805dd73ecb7, I accidentally
introduced a new way for duplicate directory entries to be returned
from readdir().  That patch fails to properly decrement the nlupgs
counter when breaking out of the inner-for loop.  This accounting
error causes an extra iteration of the inner-for loop when processing
the next cfs page and a bad ldp_hash_end value is then saved in the
lu_dirpage.  To fix this, always decrement the nlupgs counter on
entry into the inner loop.

Note: this bug only affects architectures with > 4k-sized pages, e.g.
PowerPC.

Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-3182
Lustre-change: http://review.whamcloud.com/6405
Signed-off-by: Ned Bass <bass6@llnl.gov>
Reviewed-by: Fan Yong <fan.yong@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Signed-off-by: Peng Tao <tao.peng@emc.com>