Remove the useless next link for volumes, transfers and backups

Remove the useless next link for volumes, transfers and backups

Two cases this patch will resolve:
1) Currently if the number of items equals the osapi_max_limit or
the last page of items equals the osapi_max_limit without the
parameter limit set in the user request, a next link is generated
in the response, though this next link will return empty volume
list. In fact it is unnecessary to generate the next link in
this case.

2) If the number of items equals the osapi_max_limit and limit is
greater than osapi_max_limit, a next link is generated. Actually,
the next link does not need to be generated, because it is certain
that there is no more volumes left in the database.

The method _get_collection_links has been called in volumes,
volume_transfers and backups. The patch can only affect the next
link generation for three of them. However, other lists like
consistency groups, qos specs, cgsnapshots have not implemented the
generation for the next link. Potentially this can be a wishlist
item for them.

Change-Id: I0f1f449c73d51675281497a095d869c1e72c889f
closes-bug: #1350558