chore(run-tests-container): obsolete param --skip-build removed
    
    By default, container will be re-used and not re-created on every test run.
    This makes '--skip-build' obsolete, to force the build of a new image,
    '--rebuild' and '--rebuild-code' can be used.
    
    Signed-off-by: Dominik Wombacher <dominik@wombacher.cc>