LU-3467 target: move OUT to the unified target code

LU-3467 target: move OUT to the unified target code

- Move OUT handler to the unified target code, so it can be
  used by both MDS and OST.
- Make OFD able to handle OUT requests.
- Rename MDS_MDS_PORTAL to the OUT_PORTAL and MDS_OUT_... defines
  just OUT_... since they are independent from MDS now.

Signed-off-by: Mikhail Pershin <mike.pershin@intel.com>
Change-Id: I3d595f18245f1db2619b7d15f94e4b61e882f114
Reviewed-on: http://review.whamcloud.com/6763
Tested-by: Hudson
Reviewed-by: Alex Zhuravlev <alexey.zhuravlev@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>