LU-7579 osd: move ORPHAN/DEAD flag to OSD

LU-7579 osd: move ORPHAN/DEAD flag to OSD

If a directory is unlinked while it is opened, then
it will set LUSTRE_ORPHAN_FL flag to osd object, so
the remote target can get this status by dt_attr_get().

And also LUSTRE_ORPHAN_FL will be stored inside
LMA (converted to LMAI_ORPHAN). In the meantime,
it will remove LUSTRE_SLAVE_DEAD_FL flag for dead
stripes of a striped directory, i.e. all of
dead directories (stripes) will use LMAI_ORPHAN
in LMA to indicate the status.

Also in osp_xattr, it should retrieve the return
value from the reply, which is the real length of
EA, instead of using reply buffer length.

Change-Id: I14e933b5f008981cbacbdfa478e4ec8cbebf97dc
Signed-off-by: Di Wang <di.wang@intel.com>
Reviewed-on: http://review.whamcloud.com/18024
Reviewed-by: John L. Hammond <john.hammond@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>