base/pre.yaml: Fix ansible-galaxy path

Change-Id: I462be86b367f66ddbc430f0579b247abddd70064
diff --git a/playbooks/base/pre.yaml b/playbooks/base/pre.yaml
index c81e43e..761d15f 100644
--- a/playbooks/base/pre.yaml
+++ b/playbooks/base/pre.yaml
@@ -10,7 +10,7 @@
         zuul_log_url: "https://spfactory.storpool.com/logs"
 
     - name: Install ansible collection ansible.posix
-      command: ansible-galaxy collection install ansible.posix
+      command: /var/lib/zuul/ansible-bin/2.9/bin/ansible-galaxy collection install ansible.posix
 
 - hosts: all
   tasks: