Use sizelimit from oslo.middleware

Module sizelimit in nova and oslo.middleware is the same, so
switch nova to use RequestBodySizalimiter from oslo.middleware
lib

Replace RequestBodySizalimiter and LimitingReader by temporal
aliases of this classes in oslo.middleware due to failures in grenade
jobs. Remove tests for this module

Change-Id: I6296215857c2b16035c9081e13ac4345ed5c420a
Merge "Use sizelimit from oslo.middleware"