<admin/stats> add unit tests, fix a bug

Bug was that all nodes would be considered inactive
because it was not requesting the district_active fact.

Removed model/admin coverage exclusion. There were some
pieces of code that were too hard to exercise, will be left
for integration tests that can create users and apps for
the purpose.
<admin/stats> functional test to cover db scan method
<admin/stats> should fix oo-stats bug 988554

https://bugzilla.redhat.com/show_bug.cgi?id=988554
oo-stats throws exception - not clear what cart name was causing the
break, but this should fix it.
Merge pull request #3273 from sosiouxme/admin-stats-tests

Merged by openshift-bot