Use dedicated config file for config generator

Change-Id: I1c9dcdb118005e10bc180afe8c81c8567c0b4c7b

config-generator.conf

@@ -0,0 +1,8 @@
+[DEFAULT]
+output_file = example.conf
+namespace = ironic_inspector
+namespace = ironic_inspector.common.swift
+namespace = ironic_inspector.plugins.discovery
+namespace = keystonemiddleware.auth_token
+namespace = oslo.db
+namespace = oslo.log

tox.ini

@@ -42,15 +42,7 @@ commands =
 
 [testenv:genconfig]
 envdir = {toxworkdir}/venv
-commands =
-    oslo-config-generator \
-    --output-file example.conf \
-    --namespace ironic_inspector \
-    --namespace keystonemiddleware.auth_token \
-    --namespace ironic_inspector.common.swift \
-    --namespace ironic_inspector.plugins.discovery \
-    --namespace oslo.db \
-    --namespace oslo.log
+commands = oslo-config-generator --config-file config-generator.conf
 
 [flake8]
 max-complexity=15