Update Docker container at workflow start
Update Docker container at workflow start

Should avoid potential problems with running with outdated
containers--since we aren't using the container that corresponds with
each commit, conceivably someone could get an outdated container if
they've used CAT before and haven't done a docker pull lately.

ucsc-mus-strain-cactus/Comparative-Annotation-Toolkit,ComparativeGenomicsToolkit/Comparative-Annotation-Toolkit,ComparativeGenomicsToolkit/Comparative-Annotation-Toolkit