CI: Bump kayobe-overcloud-base timeout to 3 hours

Ubuntu jobs have been much slower for the last two weeks. While we
investigate the issue, bump timeout of kayobe-overcloud-base to 3 hours
to reduce the number of failed builds.

We are hitting timeouts on the kayobe-overcloud-upgrade-base job too,
but we cannot bump beyond 3 hours because this is the maximum in the
OpenDev Zuul instance.

Change-Id: I4c8da47c28608f2bb1b768cc7f5f9d7b7c43bbbf
Signed-off-by: Pierre Riteau <pierre@stackhpc.com>

zuul.d/jobs.yaml

@@ -170,7 +170,7 @@
       Configures the primary VM as an overcloud controller.
     pre-run: playbooks/kayobe-overcloud-base/pre.yml
     run: playbooks/kayobe-overcloud-base/run.yml
-    timeout: 7200
+    timeout: 10800
 
 - job:
     name: kayobe-overcloud-centos10s