LU-669 mea.c unconditionally uses ldiskfs hashs

LU-669 mea.c unconditionally uses ldiskfs hashs

Remove the ldiskfs hash code from mea.c as described by
comment 15 in Lustre bugzilla 22410.  The MEA_MAGIC_HASH_SEGMENT
case has been replaced with a CERROR() which will indicate if
this ever occurs.

"Yes, the two level hashing function is implemented in this patch.
And there no ldiskfs hash dependency on client anymore, so those
ldiskfs hash function can be removed from mea.c"
    -- wangdi

This was originally filed as Lustre bugzilla 22410.

With the removal of this code the ldiskfsfs_dirhash() function
no longer has any consumers in obdclass.  It is now only used
by the ldiskfs osd.  Since this functionality was originally
copied from ldiskfs it makes sense to remove it entirely and
have the osd rely on the ldiskfs implementation.

Change-Id: I017918cad57fc0641ebbd9471cb5b5717c65dea2
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-on: http://review.whamcloud.com/1350
Reviewed-by: wangdi <di.wang@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Hudson
Tested-by: Maloo <whamcloud.maloo@gmail.com>