Metrics collection

This script will collect a DC's total desired and actual when run. 

**TODO**:
- [ ] Collect pending also
- [ ] Tests
- [ ] Dump the data to Cloud metrics
Non-blocking, as this can be changed later, but since the convergence function seems to need to know about servers in ERROR state and possibly other states too, should the state filtering be done in another step?  Alternately can it be passed in as an arg?