Fix inventory report aggregation

The inventory consumption stats did not previously make use of the
default consumptions since they were aggregating data directly from SQL.

This is definitely slower than the original approach, though, but I did
a similar thing for the Stock Status report (should have done this one
then as well...).
Merge branch 'master' into inventory-defaults

Conflicts:
	corehq/apps/reports/commtrack/data_sources.py
Merge pull request #3308 from dimagi/inventory-defaults

Fix inventory report aggregation