Revert the config split change

Revert the changes in a207d97 and 9a2efb3, at this moment, some code
relies on both settings from frontend and backend, and it's inconvenient
to run unittests with config split up to frontend only and backend
only.

setup.py

@@ -66,8 +66,7 @@ setup(
             "/etc/module-build-service/",
             [
                 "conf/cacert.pem",
-                "conf/web_config.py",
-                "conf/backend_config.py",
+                "conf/config.py",
                 "conf/koji.conf",
                 "conf/mock.cfg",
                 "conf/yum.conf",