Install virtualenv with pip, for documentation/testing jobs

Change-Id: Ie2979c4b4743cf7735a895d00e9ea21e0b1c3ef7
diff --git a/packer/provision/basebuild.sh b/packer/provision/basebuild.sh
index ff12b60..35f05c4 100644
--- a/packer/provision/basebuild.sh
+++ b/packer/provision/basebuild.sh
@@ -83,7 +83,8 @@
         robotframework \
         robotframework-httplibrary \
         robotframework-requests \
-        robotframework-sshlibrary
+        robotframework-sshlibrary \
+        virtualenv
         # end of pip install list
 
     # install npm modules