Default to requests cert bundle instead of nothing

[Rob Crittenden]

If no CA certificate was provided to a glance client call then verify is set to None which generally results in failure because there are no CA certs at all to validate against. It should instead default to requests.certs.where() to use the per-platform system bundle.

From certs.py:

"This module returns the preferred default CA certificate bundle.

If you are packaging Requests, e.g., for a Linux distribution or a managed
environment, you can change the definition of where() to return a separately
packaged CA bundle."

In Fedora/RHEL this is set to /etc/pki/tls/certs/ca-bundle.crt

In Ubuntu 14.04 and Debian Wheezy it is set to /etc/ssl/certs/ca-certificates.crt

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/117247
Committed: https://git.openstack.org/cgit/openstack/python-glanceclient/commit/?id=929a72e76fe1dd72e8fa28a8e3e1b574a6c19973
Submitter: Jenkins
Branch: master

commit 929a72e76fe1dd72e8fa28a8e3e1b574a6c19973
Author: Rob Crittenden <email address hidden>
Date: Tue Aug 26 18:12:19 2014 -0400

    Default to system CA bundle if no CA certificate is provided

    If no CA certificate is provided to be used for validation then
    fall back to the system-wide CA bundle as presented by
    python-requests.

    Change-Id: I05206a868150d4b62b6f1b833310eb9b86b7c4f8
    Closes-bug: #1362179