rose test-battery: fixes for off site empty configuration run

Ran the test battery off site on an old laptop with Ubuntu 12.04 installed, and identified several issues.

* `rose.config_dump`: Should not use `file` as an identifier, as it is a Python built-in.
* `rose.config_dump`: `filecmp.cmp(t.name, file_name, shallow=False)` requires the `shallow` argument to ensure that the actual contents are compared.
* `rose.task_env`: sorted glob to guarantee the same sequence.
* ` t/rose-task-run/03-app-prune.t`: `my_task_2` does not run with no `job_host`.