zuul: pin GitPython <2.1.2

See: gitpython-developers/GitPython#605

This change also fixes the nodepool health check where the last
image includes the jenkins repository which trigger an unexpected
update of jenkins when slave image is prepared

Change-Id: I60c919cdd987a9f3b8556b8e5f92f0f169cc392c

Author: TristanCacqueray

Diff for: ansible/roles/sf-zuul/tasks/install.yml

@@ -13,6 +13,7 @@
     - virtualenv /srv/zuul
     - /srv/zuul/bin/pip install --upgrade pbr pip
     - sed -i 's/^pbr.*//' requirements.txt
+    - sed -i 's/^GitPython.*/GitPython>=0.3.3,<2.1.2/' requirements.txt
     - /srv/zuul/bin/pip install -rrequirements.txt
     - /srv/zuul/bin/pip install python-swiftclient python-keystoneclient
     - /srv/zuul/bin/python setup.py install