Add homebrew curl-ca-bundle path to CA_CERTS_PATH. This will make Libcloud
use homebrew curl ca bundle file (if available) for server certificate
validation.

Contributed by Robert Chiniquy, part of LIBCLOUD-324.


git-svn-id: https://svn.apache.org/repos/asf/libcloud/trunk@1480063 13f79535-47bb-0310-9956-ffa450edef68