Remove redundant namespace

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Extract interchangable Dea/Diego backends

- Both backends have the same interface
- Also stop publishing the `droplet.updated` message since this was for the old HM
- [#76089928] & [#75217152]

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>