Add additonal Tag for critical third-party-vulnerabilities

If vulnerabilities (CVE---) exists in the base (FROM Keyword in the dockerfile)
which was fixed from vendor.

The images on MariaDB side will be updated , but customer will not get the fixed image.

Main reason is, that the Tag was not changed, because the vulnerabilities are not in MariaDB
applications, so certainly the versionsnumber not changed, so also the Tag was not changed.

So the idea is to add a sort of number for build image version, so an automatic update can be established , if a new build of a MariaDB docker image exists for the same Maxscale version.