run-base: allow git into system-config

This section runs as root, but the system-config repo is cloned as
Zuul.  This causes a problem for tox, when it installs it calls out to
git which is no longer operates in the directory [1].

[1] 8959555cee

Change-Id: I5c67208c025d29435dcc40c5eeb3b3aa8e5c4d5d

playbooks/zuul/run-base.yaml

@@ -156,6 +156,9 @@
               - name: Screenshots
                 url: "bridge.openstack.org/screenshots"
 
+    - name: Allow PBR's git calls to operate in system-config, despite not owning it
+      command: git config --global safe.directory /home/zuul/src/opendev.org/opendev/system-config
+
     - name: Run and collect testinfra
       block:
         - name: Run testinfra to validate configuration