Update Header files

src/vnt_manager/client/VNTManagerClient.py

src/vnt_manager/client/__init__.py

src/vnt_manager/requirements.in

src/vnt_manager/service/VNTManagerService.py

src/vnt_manager/service/VNTManagerServiceServicerImpl.py

src/vnt_manager/service/__init__.py

src/vnt_manager/service/__main__.py