ocfs2: Always update xattr search when creating bucket.

When we create xattr bucket during the process of xattr set, we always
need to update the ocfs2_xattr_search since even if the bucket size is
the same as block size, the offset will change because of the removal
of the ocfs2_xattr_block header.

Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Mark Fasheh <mfasheh@suse.com>