Update unit tests with an option to use a proxy

Edit: I was able to resolve the proxy issue without having to make changes to the code. Marking as obsolete for now since there are no other reports of proxy issues.

Currently, it appears that two of the unit tests may have issues executing for testers who are behind a strict internal/company firewall. We need to update the unit tests so that testers can easily set a proxy if desired. The problematic tests try to hit www.openstack.org in the following file: /OpenStackPHP/openstack-sdk-php/test/Tests/CURLTransportTest.php.

All other tests were executed successfully without use of a proxy.