Branch HEAD

b=13828
i=adilger,shadow

attachment #13289:
Don't use kernel's ATTR_* attributes over the network since the client and
MDS may run different kernels. Instead, use MDS_ATTR_* attributes (defined
in lustre_idl.h) for sa_valid.

attachment #13342:
- use a higher value for ATTR_CTIME_SET
- define MDS_ATTR_* in hex
- improve attr_unpack/attr_pack/mds_pack_open_flags