Drop os-ken dependency

* Switch to python-docker library to start containers
* Switch to FRR image
* Improve bgp output parsing by using json
* Allow to run tests on multinode environment.
* Allow to run tests from tesmest running in container.
* Move base tests to ipv4 tests.

Related-Prod: PRODX-31417
Change-Id: Ic78a3b5d092aa9a6fd8343a856ef188dafe70b49
16 files changed