OS_CACERT is set in openrc even when it has not been created

[Clint Byrum]

This is usually just ignored because OS_CACERT is only used when a client is trying to establish an SSL session. But the library shade tries to be a bit more user-friendly and give users early clues about configuration problems. When used with devstack it fails early because the file mentioned in OS_CACERT does not exist.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/180340

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/180340
Committed: https://git.openstack.org/cgit/openstack-dev/devstack/commit/?id=52a3bebcfcb09ec2b78d0357f1a074458ab04053
Submitter: Jenkins
Branch: master

commit 52a3bebcfcb09ec2b78d0357f1a074458ab04053
Author: Clint Byrum <email address hidden>
Date: Tue May 5 15:00:03 2015 -0700

    Do not set OS_CACERT if there is no CA cert

    In openrc, if we set OS_CACERT, some things will expect it to be there
    in pre-flight checks. But it may very well be missing. This "fails
    closed" because if we find the file, we try to use it, but if we don't
    find the file, and the user thought we should be using it, we'll just
    not be able to verify the server's name, and the libs will fail on that.

    Change-Id: Ia5d06afa74bc645c2f19711cfa37e57a377c329b
    Closes-Bug: #1452036