Access Tempest config.CONF directly

This ensures that all Tempest plugin configs are loaded. Accessing it
via heat_tempest_plugin.config.CONF assumed that something else was
loading the plugin configs before we tried to access it. This is
probably only the case when running Tempest itself, but we want to be
able to discover and run tests from the heat_integrationtests without
going through Tempest.

Change-Id: I5e9325766ce166e62c731330c462c030cb1e11fc
4 files changed