After JDK-8333144 docker related tests do not work on manually configured distros other than the 'standard' Ubuntu. This is because the basic generated Dockerfile with the change from JDK-8333144 assumes 'apt-get' being available, which is not the case when one runs the testing on RPM based distributions. This isn't easily noticeable unless one inspects the skipped status of a test or looks at the corresponding jtr file. When the basic container image isn't buildable, the test is skipped and not run at all.
 
So it is necessary to make the libubsan1 installation optional.