Avoid deprecation warnings coming from terra

What is the expected behavior?

The test suite currently emits several deprecation warnings, mostly due to the use of qiskit.compile(), which is to be deprecated in 0.9. We should move the tests to use the new transpilation workflow accordingly.

[jwoehr]

You mean I’m actually going to have to think?! No fair! 😃 Thanks for the help, @diego-plan9 , I’ll continue to work on this.

[diego-plan9]

Cool, thanks again! I’d suggest tackling them in separate PRs, even if both are test-related.

I am not quite clear on how the test harness works to run the tests. What should I explore, please?

Usually the output of running make test locally would work - even if it might be a bit messy. Failing that, another way would be to look at the travis logs - for example, the latest master commit at https://travis-ci.com/Qiskit/qiskit-ibmq-provider/jobs/190031347 shows warnings such as:

test_qobj_headers_in_result_sims (test.ibmq.test_ibmq_backends.TestIBMQBackends)
Test that the qobj headers are passed onto the results for sims. ... /home/travis/build/Qiskit/qiskit-ibmq-provider/qiskit-terra/qiskit/tools/compiler.py:50 *DeprecationWarning: qiskit.compile() is deprecated and will be removed in Qiskit Terra 0.9. Please use qiskit.transpile() to transform circuits and qiskit.assemble_circuits() to produce qobj.

Those lines would hopefully point towards where the deprecated instruction is being used (test.ibmq.test_ibmq_backends.TestIBMQBackends.test_qobj_headers_in_result_sims), and hints on what the new behaviour is (in this case, replacing the compile(..) at 97).