Add pagination to backups

Add pagination to backups

Backups list/detail does not support pagination now.
Add pagination support like volume does by using marker,
limit, sort_key and sort_order.

Partial-Implements: blueprint extend-limit-implementations

DocImpact
APIImpact
Use marker, limit, etc. in list url like volume does.

(Pulled from gate, cinder can no longer pass unit tests)

Change-Id: I33dbdc34c61f78eab2a78a9cda08780068867a03