Remove double config rsync for Java apps

This was introduced in a43cc202 (along with a separate unrelated feature).

However it didn't test whether app_config_dir and app_xml_config_dir were
actually the same path. Resulting, for most cases, in the same rsync command
being run twice.

I'm slimming this down by allowing env.config_dir_name to override the
config path but otherwise falling back to env.project_name, then removing
the second rsync altogether.

This shouldn't introduce any regressions. But if it does, it will only by
for applications that are no longer in use or development.