[WIP] Multi-vdu, multi-charm support

This work-in-progress adds support + integration testing for multi-vdu, multi-charm VNFs

TODO:
- Resolve race condition causing some tests to hang or not clean up
properly

Signed-off-by: Adam Israel <adam.israel@canonical.com>
Change-Id: Ibb6c93bb622c5807ed136cabc0c3b1cfcc50bdbf