885128 - pulp.plugins.loader.api should use the "db" logger.
885128 - Altered two more files to use the 'db' logger.

Also, changed some logging statements to DEBUG from INFO, because they
makes the logs noisy during migrations, and they are not informative for
end users.
Merge pull request #243 from pulp/rbarlow-885128

Rbarlow 885128