NFSv4.1: Clean up layout segment comparison helper names

Give them names that are a bit more consistent with the general
pNFS naming scheme.

 - lo_seg_contained -> pnfs_lseg_range_contained
 - lo_seg_intersecting -> pnfs_lseg_range_intersecting
 - cmp_layout -> pnfs_lseg_range_cmp
 - is_matching_lseg -> pnfs_lseg_range_match

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>