LU-1665 libcfs: alignment of hsb_head[0] can be suboptimal

LU-1665 libcfs: alignment of hsb_head[0] can be suboptimal

On ia64, hsb_head[0] of struct cfs_hash_bucket could be aligned to a
4-byte boundary.  However, after allocating the hash bucket and
casting, the first member of the struct pointed to by hsb_head[0]
might prefer an 8-byte alignment.  This causes a constant stream
of unaligned access warnings from the kernel.

For other cpus this might waste some small amount of space, but
potentially produces more natural alignments (8 byte objects on 8
byte boundaries).

Signed-off-by: chas williams - CONTRACTOR <chas@cmf.nrl.navy.mil>
Change-Id: I4561ab3e6553b5dcef840b8e4e9aa3023b7c3586
Reviewed-on: http://review.whamcloud.com/4965
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Tested-by: Hudson
Reviewed-by: Keith Mannthey <keith.mannthey@intel.com>
Tested-by: Maloo <whamcloud.maloo@gmail.com>