heat api paste.ini auth_uri should use auth_port

For token based auth to work, the auth_uri needs to use
auth_port, which points at the internalURL of the keystone
service, the current config uses publicURL which causes
token auth requests to keystone to fail

ref bug 1072944

Change-Id: If7e0c2246205377f57f879ccf8bf36ff8b0d92e1
Signed-off-by: Steven Hardy <shardy@redhat.com>