Add become:true to virtualenv installation task

This commit adds a 'become: true' to the 'package' task responsible
for installing virtualenv. Depending on the environment this is
likely required/mandatory.

Additional background: https://review.opendev.org/#/c/656933

Change-Id: Ifc1d56cda2e3b32dedd2dd5637fc5e647dd148cc

roles/build-test-packages/tasks/main.yml

@@ -50,6 +50,7 @@
 
 - when: virtualenv_exist.rc != 0
   name: Install virtualenv
+  become: true
   package:
     state: present
     name: >