Redmine#4683: ensure dynamic inputs from data containers work

see https://cfengine.com/dev/issues/4683

Test is in staging.

Current output:

```
2014-02-24T16:54:00-0500    error: Can't parse directory './15_control/01_common/'.
2014-02-24T16:54:00-0500    error: Policy failed validation with command '"/home/tzz/source/cfengine/core/tests/acceptance/workdir/__15_control_01_common_inputs_from_json_cf/bin/cf-promises" -c "./15_control/01_common/inputs_from_json.cf"'
```