Use abstracted virtualenv_command from ensure-pip

This will use venv and Python 3 on platforms where that is supported.

Change-Id: I8293d3299e47e9221d37eb36db6ce5f056824b0e

playbooks/bindep/run.yaml

@@ -1,4 +1,6 @@
 - hosts: all
+  roles:
+    - ensure-pip
   vars:
     bindep_profile: test
   tasks:
@@ -6,12 +8,14 @@
       pip:
         chdir: "{{ zuul_work_dir }}"
         virtualenv: "{{ zuul_work_virtualenv }}"
+        virtualenv_command: "{{ ensure_pip_virtualenv_command }}"
         requirements: requirements.txt
 
     - name: Install the project from source
       pip:
         chdir: "{{ zuul_work_dir }}"
         virtualenv: "{{ zuul_work_virtualenv }}"
+        virtualenv_command: "{{ ensure_pip_virtualenv_command }}"
         name: .
 
     - name: Run bindep with the file