Pin DIB to Python 2 compatible version on py2 jobs

Diskimage-builder dropped Python 2 support in 3.0.0. We need to pin the
-py2 jobs to a Python 2 compatible version. We set to 2.30.0 as per
latest upper-constraints.txt [1].

Note that Python 3 devstack installs will also have to be pinned to same
version because stable/stein devstack ensures that all libs being used
for development are installed under both versions of Python [2].

[1] https://opendev.org/openstack/requirements/src/commit/4ae10f52cec8f6d870c7d862d22c66a64ce74f9f/upper-constraints.txt#L612
[2] https://opendev.org/openstack/devstack/src/commit/ab86ced64cb6c053cf3340ab4d8a1d988a6b76c4/inc/python#L379-L388

Change-Id: Ib9954b8d634fc791e8cf0da73ad76ac8ff3e85b8
diff --git a/zuul.d/jobs.yaml b/zuul.d/jobs.yaml
index 60d9150..38b2d04 100644
--- a/zuul.d/jobs.yaml
+++ b/zuul.d/jobs.yaml
@@ -463,6 +463,9 @@
     vars:
       devstack_localrc:
         USE_PYTHON3: False
+    required-projects:
+      - name: openstack/diskimage-builder
+        override-checkout: 2.30.0
 
 - job:
     name: octavia-v2-dsvm-scenario-stable-train
@@ -473,6 +476,9 @@
     name: octavia-v2-dsvm-scenario-stable-stein
     parent: octavia-v2-dsvm-scenario
     override-checkout: stable/stein
+    required-projects:
+      - name: openstack/diskimage-builder
+        override-checkout: 2.30.0
 
 # Legacy jobs for the transition to the act-stdby two node jobs
 - job:
@@ -504,6 +510,9 @@
           USE_PYTHON3: False
           LIBVIRT_TYPE: kvm
           LIBVIRT_CPU_MODE: host-passthrough
+    required-projects:
+      - name: openstack/diskimage-builder
+        override-checkout: 2.30.0
 
 - job:
     name: octavia-v2-act-stdby-dsvm-scenario-two-node
@@ -589,6 +598,9 @@
     name: octavia-v2-dsvm-tls-barbican-stable-stein
     parent: octavia-v2-dsvm-tls-barbican
     override-checkout: stable/stein
+    required-projects:
+      - name: openstack/diskimage-builder
+        override-checkout: 2.30.0
 
 - job:
     name: octavia-v2-dsvm-tls-barbican-stable-rocky
@@ -621,6 +633,9 @@
     vars:
       devstack_localrc:
         USE_PYTHON3: False
+    required-projects:
+      - name: openstack/diskimage-builder
+        override-checkout: 2.30.0
 
 - job:
     name: octavia-v2-dsvm-spare-pool-stable-train
@@ -631,6 +646,9 @@
     name: octavia-v2-dsvm-spare-pool-stable-stein
     parent: octavia-v2-dsvm-spare-pool
     override-checkout: stable/stein
+    required-projects:
+      - name: openstack/diskimage-builder
+        override-checkout: 2.30.0
 
 - job:
     name: octavia-v2-dsvm-cinder-amphora
@@ -723,6 +741,9 @@
     vars:
       devstack_localrc:
         USE_PYTHON3: False
+    required-projects:
+      - name: openstack/diskimage-builder
+        override-checkout: 2.30.0
 
 - job:
     name: octavia-v2-act-stdby-iptables-dsvm-py2-scenario-centos-7
@@ -766,3 +787,6 @@
     name: octavia-v2-act-stdby-dsvm-scenario-stable-stein
     parent: octavia-v2-act-stdby-dsvm-scenario
     override-checkout: stable/stein
+    required-projects:
+      - name: openstack/diskimage-builder
+        override-checkout: 2.30.0