The locate and authdata pluggable interfaces are older than the plugin framework code, and does not honor plugin_base_dir or any other profile variable, so there is no way to prevent test programs from loading and being affected by locate plugin modules in the install tree. The authdata interface should be converted to use the new plugin framework, which we can do without any backwards compatibility since it is not public. (It might even be reasonable to eliminate it.) The locate interface is public, so needs to be treated more carefully.