Update http links in docs

This patch is proposed according to the Direction 10 of doc
migration(https://etherpad.openstack.org/p/doc-migration-tracking).

Change-Id: I0061bf788a8da89da0077db63f6cecf2ead0d0be

Author: huangshan

CONTRIBUTING.rst

@@ -1,13 +1,13 @@
 If you would like to contribute to the development of OpenStack,
 you must follow the steps documented at:
 
-   http://docs.openstack.org/infra/manual/developers.html#development-workflow
+   https://docs.openstack.org/infra/manual/developers.html
 
 Once those steps have been completed, changes to OpenStack
 should be submitted for review via the Gerrit tool, following
 the workflow documented at:
 
-   http://docs.openstack.org/infra/manual/developers.html#development-workflow
+   https://docs.openstack.org/infra/manual/developers.html#development-workflow
 
 Pull requests submitted through GitHub will be ignored.
 

doc/source/index.rst

@@ -29,7 +29,7 @@ Release Notes
 .. toctree::
    :maxdepth: 1
 
-   Release Notes <http://docs.openstack.org/releasenotes/python-openstackclient>
+   Release Notes <https://docs.openstack.org/releasenotes/python-openstackclient/>
 
 Contributor Documentation
 -------------------------