Remove ratelimit from v3 api

[Alex Xu]

The ratelimit middleware isn't really useful. that point out by https://review.openstack.org/#/c/34821/

So we can remove ratelimit from v3 api. And after discussion from mail-list:
http://lists.openstack.org/pipermail/openstack-dev/2013-November/020291.html

there isn't any one and any reason object it.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/58713

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/58713
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=93d3e47531942243676342e10f569cda396a42c5
Submitter: Jenkins
Branch: master

commit 93d3e47531942243676342e10f569cda396a42c5
Author: He Jie Xu <email address hidden>
Date: Wed Nov 27 17:32:28 2013 +0800

    Remove middleware ratelimits from v3 api

    The ratelimit middleware isn't really useful. That is pointed out
    by https://review.openstack.org/#/c/34821/. And it didn't get any
    object from mail-list:
    http://lists.openstack.org/pipermail/openstack-dev/2013-November/020291.html

    This patch remove ratelimit middleware and limits extension. The config option
    'api_rate_limit' is only valid in v2 api. The pipeline factory for v3 api won't
    check that option anymore. For compatibility, if user is still using old
    'api-paste.init', pipeline factory will ignore to load ratelimit middleware, and
    print warning message to user for notice ratelimit is deprecated in v3 api.

    Closes-bug: 1255471
    DocImpact

    Change-Id: Ifeae0504e11089f95e4d8af58bcb7372dca87f81