Templates shouldn't have region option populated

When submitting a template in the Dataflow UI, it is necessary to specify a region.

If the template also has an erroneously set region in its PipelineOptions, then the workers are not able to communicate with the service.

If we're creating a template (i.e. template_location != null), then we shouldn't populate the region.

This is an issue in Python, and likely in JAva as well. This issue hit https://stackoverflow.com/questions/47093294/templated-dataflow-hangs-over-an-hour-at-loading-and-quits-with-an-error

Imported from Jira [BEAM-3148](https://issues.apache.org/jira/browse/BEAM-3148). Original Jira may contain additional context.
Reported by: pabloem.

Start by tracing template submission in the Python SDK where template_location and PipelineOptions region are handled, then check the corresponding Java path. Reproduce the Dataflow template case and verify that a template with an existing region does not populate or retain that region, while normal submissions still require it.

Written by the indexing model from the issue text.