Set default service_type to "data-processing" in client

We're using the default value in many places, so, we should switch it
to the data-processing by default. The fallback mechanism is already
implemented, so, backward compatibility supported.

It's needed to make CLI support both endpoints.

Change-Id: I8818c77a96685c8a557aa6fec77002c93064118e
Partial-bug: #1356053
Merge "Set default service_type to "data-processing" in client"