fix: Add pubsub emulator support to schemas

[bealsao]

Hi All,

This is a submission to resolve issue #647 that I submitted.

The schema_service/client.py did not receive the fixes in this change: #297

So you receive the same errors as described in the issue: #290

Fixes#647

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

For more information, open the CLA check for this pull request.

[acocuzzo]

Hi @bealsao
Thanks so much. Because what you are changing is auto-generated code, we actually have to change our owlbot.py file to add the emulator support to our schema_service file, and then regenerate the library, so that this change is not reverted. I'm happy to do this in a separate PR that I'll link to the issue. Thanks again for your contribution!