Switch to TLS ZK based functional job

This switches the functional test job to the newly defined
zuul-tux-zuul-client job in the zuul repo which supports Zookeeper
TLS.  We could switch the existing job in this repo to reparent
to zuul-tox, but this change sequence is slightly easier.

Depends-On: https://review.opendev.org/777489
Change-Id: Ia5033ab2eaae038d1fa0f78605c42fa1b36adc51

.zuul.yaml

@@ -14,19 +14,6 @@
           /ZjKtC+ftXNtvtFxcsxKYD/VqFZGgc4ZtHJV1OE+2bOj436AUo3doYjrkwitX4IfZQNEs
           PdwF2MW3w/xLLbl+jQqM6tp/1snbuRK/l1rP8XFCQUlb2sZE3oCAJJNAsQNPFY=
 
-- job:
-    name: zuul-client-zuul-functional
-    parent: tox
-    description: |
-      Test that Zuul and zuul-client work together.
-    required-projects:
-      - zuul/zuul
-      - zuul/zuul-client
-    vars:
-      zuul_work_dir: "{{ zuul.projects['opendev.org/zuul/zuul'].src_dir }}"
-      tox_envlist: zuul_client
-    nodeset: ubuntu-bionic
-
 - job:
     name: zuul-client-build-image
     parent: opendev-build-docker-image
@@ -86,7 +73,7 @@
         - tox-py38:
             nodeset: ubuntu-bionic
             timeout: 3600
-        - zuul-client-zuul-functional
+        - zuul-tox-zuul-client
         - build-python-release
     gate:
       jobs:
@@ -100,7 +87,7 @@
         - tox-py38:
             nodeset: ubuntu-bionic
             timeout: 3600
-        - zuul-client-zuul-functional
+        - zuul-tox-zuul-client
         - build-python-release
         - zuul-client-upload-image
     promote: