[CI] Set 0 swap size

Infra has recently changed the way the swap works and it might
be impacting disk usage more than it used to. [1]

We should try to run our jobs without having to resort to
swap usage as it is always much slower.

[1] http://eavesdrop.openstack.org/irclogs/%23openstack-infra/%23openstack-infra.2020-11-03.log.html#t2020-11-03T15:18:01

Change-Id: Ic3e97ada11b953e28a36b9594b710bf7b09b05b7
(cherry picked from commit ba6e730)

Author: yoctozepto

zuul.d/base.yaml

@@ -43,6 +43,7 @@
       # NOTE(yoctozepto): Ansible on Debian defaults to /usr/bin/python which is
       # python2. Let's use python3 instead as expected in 2020 and beyond.
       ansible_python_interpreter: python3
+      configure_swap_size: 0
     roles:
       - zuul: zuul/zuul-jobs
       - zuul: openstack/kolla