Add python3-openvswitch to apt preferences

Author: Alex-Welsh

.github/workflows/stackhpc-container-image-build.yml

@@ -206,7 +206,7 @@ jobs:
       - name: Write apt config to file
         run: |
             cat > stackhpc-apt-preferences <<EOF
-            Package: openvswitch-switch openvswitch-common openvswitch-common-dpdk
+            Package: openvswitch-switch openvswitch-common openvswitch-common-dpdk python3-openvswitch
             Pin: version 3.3.*
             Pin-Priority: 1001
             EOF