Collect diskimage-builder logs

In the dependent change, the dib logs are stored into a separate file
by the devstack plugin.  Collect this.

Depends-On: https://review.openstack.org/612622
Change-Id: I5bc0d9a3b071733cbe31d618f7236a3c2285b3e5
diff --git a/zuul.d/jobs.yaml b/zuul.d/jobs.yaml
index d529a3b..c7c48db 100644
--- a/zuul.d/jobs.yaml
+++ b/zuul.d/jobs.yaml
@@ -65,6 +65,8 @@
       devstack_plugins:
         barbican: https://github.com/openstack/barbican.git
         neutron: https://github.com/openstack/neutron.git
+      zuul_copy_output:
+        '/var/log/dib-build' : logs
 
 - job:
     name: octavia-dsvm-noop-base