Add specific play to bootstrap python dependencies

For example, zookeeper nodes don't actually need to install the
virtualenv role because zookeeper is java.

Change-Id: I71318029fb558a7087cc2f8db625b48592615ad4
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

playbooks/bootstrap.yaml

@@ -31,6 +31,13 @@
       include_role:
         name: openstack.sudoers
 
+- name: Bootstrap python dependencies for windmill
+  hosts: all,!bastion,!zookeeper
+  # NOTE(pabelanger): Because we are currently using a single host, we need this
+  # operation to be serial. When we switch to multi-host, this can be removed.
+  serial: 1
+
+  tasks:
     - name: Setup openstack.virtualenv role
       include_role:
         name: openstack.virtualenv