Add workaround step to avoid introspection failure

This error seems to be environment/workflow specific.
The workaround was added as the error is not
reproducible in other environments - and those
not using ironic node-update.
Related-Bug: #1649350

Change-Id: Ib47be90d4cba72cc88b5d9a1ac702279354b27ff

roles/overcloud-prep-images/templates/overcloud-prep-images.sh.j2

@@ -75,6 +75,10 @@ for item in $items; do
     count=$((count+1))
 done
 
+# Temporary step to avoid introspection failure
+# Workaround for: https://bugs.launchpad.net/tripleo/+bug/1649350
+sudo mistral-db-manage populate
+
 {% endif %}