Remove default setting of 'mysql_traditional_mode'

The sqlalchemy versions we are using/supporting (0.6+)
have the detection of the mysql mode built-in so only
activate the connect setting if we are somehow overriden
by a user who knows what they are doing.

Fixes bug 1396278

Change-Id: If2226d3e9f921a1c5f62a6727016fe86cd50a9b5
Merge "Remove default setting of 'mysql_traditional_mode'"