Use `sum` instead of `samplecount` for apps dashboard
Use `sum` instead of `samplecount` for apps dashboard

We should be sending the `sum` value from the cloudwatch metrics to
Hosted Graphite instead of the `samplecount`. This will allow us to set
a default value for the metrics and remove patchy data.

alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws,alphagov/digitalmarketplace-aws