Run tests in parallel as much as possible

The rpc unit tests have dependencies between tests that make it
impossible to run them in parallel right now, and because that
module is deprecated it doesn't make sense to spend a lot of
effort fixing the problems.  In order to test the other modules
in parallel, we now do two test runs: one in parallel for
everything but rpc, and one serialized for rpc.

Closes-Bug: #1272035

Change-Id: I85ae00b0180bb6fdc760c97882e4e7901e9db2ef
Merge "Run tests in parallel as much as possible"