Update opts in Dockerfiles using ubi8 OpenJDK

[jerboaa]

The semantics of JAVA_OPTS env is that they remove any default tuning from the UBI 8 OpenJDK image. A better suggestion would be to only append the quarkus specific options to the JVM command line.

That can be done by using JAVA_OPTS_APPEND instead. Using that over JAVA_OPTS has the added benefit that users specifying JAVA_OPTS_APPEND in a deployment config would see their values show up. They wouldn't see them show up if they added an env JAVA_OPTS_APPEND, since JAVA_OPTS is specified in the Dockerfile (overriding any JAVA_OPTS_APPEND use).