Replace http with https for doc links in devstack's document

1) Update doc links according to OpenStack document migration
2) Use https instead of http for docs links

Change-Id: I81b560d1e4c5210dc00a6a6ac06c03bb1e69d595
diff --git a/doc/source/faq.rst b/doc/source/faq.rst
index a186336..ed9b4da 100644
--- a/doc/source/faq.rst
+++ b/doc/source/faq.rst
@@ -32,9 +32,9 @@
 `git.openstack.org
 <https://git.openstack.org/cgit/openstack-dev/devstack>`__ and bug
 reports go to `LaunchPad
-<http://bugs.launchpad.net/devstack/>`__. Contributions follow the
+<https://bugs.launchpad.net/devstack/>`__. Contributions follow the
 usual process as described in the `developer guide
-<http://docs.openstack.org/infra/manual/developers.html>`__. This
+<https://docs.openstack.org/infra/manual/developers.html>`__. This
 Sphinx documentation is housed in the doc directory.
 
 Why not use packages?