When public_endpoint is set but different urls are used for endpoints
(especially for admin endpoint and public endpoint), it can cause
problem with self-url detection in keystone because it always assumes
that the url should be directed to that public_endpoint even when
a request comes from admin endpoint.
This patch makes public_endpoint unset by default to avoid issues in
the deployment where admin endpoint and public endpoint are still
separated.
Related-bug: #1889017
Change-Id: Ia43e9dcd8085bbb0954b64873504398a85771032
a1a1e62012