Add virtualenv for missing depends workaround

We missed adding virtualenv to pip for our broken dependencies.

Change-Id: Iac68712906b5cd7e993d0b763ff90224d154edb3
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

tasks/install.yaml

@@ -33,6 +33,7 @@
   become: yes
   pip:
     name: "{{ item }}"
+    virtualenv: "{{ zuul_pip_virtualenv|default(omit) }}"
   with_items:
     - jenkins-job-builder
     - pyzmq