Cannot run office test with Jetty:9 servlet engine

The docker image of Jetty:9 is based on openjdk:jdk-15 which is itself based on oraclelinux-8. And this image is based on a red hat, not on a Debian, which means apt-get command cannot be used to install the packages, as we're doing for installing the specific version of LibreOffice.

Moreover with oraclelinux-8 yum is no longer available in favor of microdnf (see: https://github.com/docker-library/openjdk/pull/425) so we probably need to support the three package manager to be safe.