Test the number of sql queries.
Add a test checking for users and packages.
Cut down on the number of queries.

For the first insert, there are 7 sql statements.  They are:
- check if the user exists
- create the user
- check if the package exists
- create the package
- create the message
- associate the message with the user
- associate the message with the package

Then, for the second insert, there are 3 more sql statements:
- create the message
- associate the message with the user
- associate the message with the package

Should hopefully be an improvement.
Clear up what the "_cache" is for.
Also cleanup in the other component tearDown methods.
Merge pull request #70 from fedora-infra/feature/optimized-insert

Cut down on the number of queries.