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.
Merge pull request #19 from YellLabs/java_double_rsync

Remove double config rsync for Java apps