Increase the DIB DHCP timeout to 60

We seem to be hitting occasional failures to DHCP in time, although
DHCP itself seems working. Try increasing timeout from 30 to 60.

Change-Id: I0cc0af440f954007f01bae4508f6853e1529913d
Depends-On: https://review.opendev.org/684765

roles/ipa-build-dib-image/tasks/main.yaml

@@ -6,6 +6,8 @@
   command: |
     ironic-python-agent-builder -e dhcp-all-interfaces -o {{ image_name }} {{ image_distro }}
   environment:
+    # Increase from the default value of 30
+    DIB_DHCP_TIMEOUT: 60
     # Use repositories checked out by Zuul
     DIB_REPOLOCATION_ironic_python_agent: '{{ ipa_source_path }}'
     DIB_REPOREF_ironic_python_agent: HEAD