etsi_bwm fixes and unit tests

scripts/run_tests_locally-etsi_bwm.sh

src/common/tests/MockServicerImpl_Context.py

src/nbi/.gitlab-ci.yml

...nbi/service/rest_server/nbi_plugins/etsi_bwm/Resources.py

src/nbi/service/rest_server/nbi_plugins/etsi_bwm/Tools.py

src/nbi/service/rest_server/nbi_plugins/etsi_bwm/__init__.py

src/nbi/tests/Constants.py

src/nbi/tests/PrepareTestScenario.py

src/nbi/tests/data/topology-dummy.json

src/nbi/tests/test_etsi_bwm.py