LU-12914 mdt: mdt_prep_ma_buf_from_rep() is called twice

LU-12914 mdt: mdt_prep_ma_buf_from_rep() is called twice

In some rare cases (replay of file open with O_LOV_DELAY_CREATE
when object found dead on mdt) mdt_prep_ma_buf_from_rep() can
be called twice (in either mdt_reint_open() and mdt_open_by_fid())
during the same request handling.
So remove assert checking if LMV or LOV has already been found and
set in ma.

Signed-off-by: Bruno Faccini <bruno.faccini@intel.com>
Change-Id: I78e0456ea59c37cab4276383c75c4fa5cc9f4829
Reviewed-on: https://review.whamcloud.com/36611
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Patrick Farrell <farr0186@gmail.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>