tox: add posargs in aio env (#2059)

allow tags in molecule
diff --git a/tox.ini b/tox.ini
index bed67e1..ca2522a 100644
--- a/tox.ini
+++ b/tox.ini
@@ -78,7 +78,7 @@
   openvswitch: ATMOSPHERE_NETWORK_BACKEND = openvswitch
   ovn: ATMOSPHERE_NETWORK_BACKEND = ovn
 commands =
-  molecule test -s aio
+  molecule test -s aio {posargs}
 
 [testenv:docs]
 envdir = {toxworkdir}/docs