Fix update-application-templates script to cope with rebuilds

The update-application-templates.sh script in integration-platform-tooling/scripts/fuse does not work if it has already completed successfully for a previous set of tags.

For example, for the 7.3.0.CR4 builds, the script had been run once successfully, producing a redhat-00001 tag on the application-templates repo. However, the ipaas-quickstarts needed to be rebuilt, and as a result, the application templates needed to be updated to reflect the new fabric8 quickstart tags. The build script couldn't distinguish between the previous completion of a successful tagging run and the fact that a new tag was needed, so it didn't update the application templates. I think a bit more logic is required in the update_application_templates function.