Make TRADITIONAL the default SQL mode

Rather than log a warning when TRADITIONAL mode is not enabled,
just make it the default. If this causes INSERTs or UPDATEs from
applications to break, it just exposes that they are inserting
broken data to begin with.

Change-Id: I84c1781454ed5f46c7a135c96bafc575f313f9bc
Merge "Make TRADITIONAL the default SQL mode"