ci: Disable functional tests

We currently run only vexxhost with nested
virtualization. Due to a kernel change all
functional jobs are failing.

Change-Id: I9ab45da36dbc5618587b4795658b4f4bb264f2c8
Signed-off-by: Spyros Trigazis <spyridon.trigazis@cern.ch>

.zuul.yaml

@@ -383,8 +383,6 @@
       jobs:
         - magnum-functional-api
         - magnum-functional-api-python2
-        - magnum-functional-k8s
-        - magnum-functional-swarm-mode
         - openstack-tox-cover:
            voting: false
         - container-build