Pin JJB to 1.6.1

To avoid breakage with JJB and zuul-launcher, we're pinning to 1.6.1.
As soon as zuulv3 is released, we nolonger need the JJB dependency.

Change-Id: Ib74396403ba0b74ba32d424f087152522e8a0f8d
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

tasks/install.yaml

@@ -32,9 +32,10 @@
 - name: Install missing pip dependencies
   become: yes
   pip:
-    name: "{{ item }}"
+    name: "{{ item.name }}"
+    version: "{{ item.version|default(omit) }}"
     virtualenv: "{{ zuul_pip_virtualenv|default(omit) }}"
   with_items:
-    - jenkins-job-builder
-    - pyzmq
+    - { name: 'jenkins-job-builder', version: '1.6.1' }
+    - { name: 'pyzmq' }
   when: zuul_install_method == 'git' or zuul_install_method == 'pip'