BoneCP leaking connections on database failure

In ConnectionHandle.markPossiblyBroken ->

When the database is down, first call from Thread1 to getIsDbDown is set to true. Concurrent Thread2, skips the check and therefore the connection is not destroyed.

In addition, a SQL connection code 08003 should be destroyed rather than flagged as possibly broken.

This will fix major issues with connection leaks that people are having with Play 2.0 and Play 2.1.