LU-5565 osd-ldiskfs: separate LASSERT() into two lines

Separate the compound assertions in osd-ldiskfs into two lines:

    LASSERT(dt_object_exists(dt) && !dt_object_remote(dt));
to
    LASSERT(dt_object_exists(dt));
    LASSERT(!dt_object_remote(dt));

so that it is possible to distinguish which of the two is being hit.

Signed-off-by: Andreas Dilger <andreas.dilger@intel.com>
Change-Id: I3ff4fc28bffe955ab051ece665faa4c8a6500c1e
Reviewed-on: http://review.whamcloud.com/12398
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>