Calling a ConfigOpts instance with new args will implicitly reset
the config values in the instance. This means that in the previous
revision of the code, any assignment of oslo_config_config to
self._local_oslo_config would be instantly clobbered by calling
self._local_oslo_config() to read from default_config_files.
Now, if oslo_config_config is set to a non-None value it will be
left unmolested. This is useful because oslo_config_config turns out
to be the ideal way to pass config to AuthProtocol when the caller
already has access to the project config object and neither global
conf nor paste is being used.
Change-Id: I0beb809bc5ace609561f10dc52800a8a6e03f7e6
Closes-Bug: #1540022
dc22e9fd30