Previously --insecure argument didn't have any effect
on discover-tempest-config's behavior which lead to to failing
requests due to certificates verify failures. That is fixed now.
Due to the change discover-tempest-config can now automatically
set the following 2 tempest options:
* CONF.identity.disable_ssl_certificate_validation - previously always
set to True by default.
* CONF.identity.ca_certificates_file - previously not set at all.
Change-Id: Iafcc9720e45190e6bd1046540d7c4a640c043023