always use clean venv for openstack

Change-Id: I54023bca8b3c02371e38e8eae3dc021fb0e802e0
diff --git a/src/com/mirantis/mk/Openstack.groovy b/src/com/mirantis/mk/Openstack.groovy
index d6c220c..1e419b3 100644
--- a/src/com/mirantis/mk/Openstack.groovy
+++ b/src/com/mirantis/mk/Openstack.groovy
@@ -22,7 +22,7 @@
  * @param version     Version of the OpenStack clients
  */
 
-def setupOpenstackVirtualenv(path, version = 'kilo') {
+def setupOpenstackVirtualenv(path, version = 'latest') {
     def python = new com.mirantis.mk.Python()
     python.setupDocutilsVirtualenv(path)
 
@@ -55,7 +55,7 @@
     } else {
         requirements = openstack_latest_packages
     }
-    python.setupVirtualenv(path, 'python2', requirements)
+    python.setupVirtualenv(path, 'python2', requirements, null, true)
 }
 
 /**