Add a test for getOldestRequestTime with an invalid identifier
fix getOldestRequestTime to use builder ids
make findBuilderId call through to the DB layer
fix the invocation of pylint
Merge pull request #1256 from djmitche/bug2940

Use builderid, not buildername, to look up buildrequests

Fixes ticket:2940
Merge sa2ajj/buildbot:fix-copy-n-paste (PR #1262)