Automate switch provisioning for each test case

[ccascone]

Like we do for PTF tests, different test cases might require different P4 programs (fabric profile) and entries. For now, we rely on a manual process, which is time-consuming and error-prone. Instead, we should make it possible to script switch provisioning.

A few options:

1. Provide p4runtime library like we do for fabric-tna's PTF tests (could be p4runtime-shell)
2. Provide stratum p4rt_write.log for each test case (hard to modify by hand) and invoke stratum-replay
3. Use STC to automate ONOS bring up and configuration (CPU/memory heavy, can only be used to program tables for which we have app logic)

Option 1 seems the best for our needs.