Pin pip docker version

Change-Id: Iee65af745b8c16e6f93acf121a0e3ba3613db288

playbooks/post.yaml

@@ -4,12 +4,13 @@
       block:
         # NOTE(SamYaple): https://github.com/ansible/ansible/issues/14131
         - command: cp -r /home/zuul/.ansible_async /logs/async_logs
-        - command: journalctl -xb -u docker.service
-          register: docker_daemon_log
-          no_log: True
-        - copy:
-            content: "{{ docker_daemon_log.stdout }}"
-            dest: /logs/docker_daemon.log
+        # FIXME(SamYaple): running this is causing the gate to hang
+        #- command: journalctl -xb -u docker.service
+        #  register: docker_daemon_log
+        #  no_log: True
+        #- copy:
+        #    content: "{{ docker_daemon_log.stdout }}"
+        #    dest: /logs/docker_daemon.log
       become: true
 
     - name: Copy logs

playbooks/setup-gate.yaml

@@ -45,6 +45,7 @@
             - python-pip
         - pip:
             name: docker
+            version: 2.7.0
         - docker_container:
             name: registry
             image: registry:2