Add flexibility for Stack creation

- Use variables for network, flavor and image.
- Make use of the config_drive for the instances.
- Allow for setting DNS servers
- Add note for workaround for Molecule bug for FQCN playbooks

Sem-Ver: feature
Change-Id: Ic3a1c1e8d0ca36926c1db41340405dd2d9bf592d
diff --git a/tox.ini b/tox.ini
index 8d42a68..5e6e482 100644
--- a/tox.ini
+++ b/tox.ini
@@ -21,7 +21,7 @@
 passenv =
     OS_*
     TERM
-    STACK_NAME
+    ATMOSPHERE_*
 
 [testenv:build]
 deps =