Use no-op drivers for Octavia in gate

Continue to test Heat's interaction with the Octavia API without relying on
Octavia's interaction with Nova, Neutron &c. which is known to be unstable.

Change-Id: I8765aceee09ada3086abc704b7f73ce240e21847

.zuul.yaml

@@ -27,7 +27,6 @@
       - ^heat/locale/.*$
       - ^heat/tests/.*$
       - ^releasenotes/.*$
-    pre-run: playbooks/get_amphora_tarball.yaml
     vars:
       disable_convergence: 'false'
       sql: mysql

playbooks/devstack/functional/run.yaml

@@ -68,6 +68,9 @@
           export DEVSTACK_LOCAL_CONFIG+=$'\n'"OCTAVIA_AMP_IMAGE_NAME=test-only-amphora-x64-haproxy-ubuntu-xenial"
           services+=,octavia,o-cw,o-hk,o-hm,o-api
           export PROJECTS="openstack/octavia $PROJECTS"
+          export OCTAVIA_AMPHORA_DRIVER="amphora_noop_driver"
+          export OCTAVIA_COMPUTE_DRIVER="compute_noop_driver"
+          export OCTAVIA_NETWORK_DRIVER="network_noop_driver"
           export PROJECTS="openstack/barbican $PROJECTS"
           export PROJECTS="openstack/python-barbicanclient $PROJECTS"
           export PROJECTS="openstack/barbican-tempest-plugin $PROJECTS"

playbooks/get_amphora_tarball.yaml

@@ -1,6 +0,0 @@
-- hosts: primary
-  tasks:
-    - name: Download amphora tarball
-      get_url:
-        url: "https://tarballs.openstack.org/octavia/test-images/test-only-amphora-x64-haproxy-ubuntu-xenial.qcow2"
-        dest: /tmp/test-only-amphora-x64-haproxy-ubuntu-xenial.qcow2