Turn off debug logging in sqlalchemy by default

This commit adds a new config option sqlalchemy_debug which is used
for enabling debug messages from sqlalchemy. Previously, this logging
was enabled whenever debug was enabled. The debug log level for
sqlalchemy prints out all SQL queries and results which is way too
verbose for most cases where just debug logging is useful. This
change disables this previous behavior by defaulting the new option
to false and decoupling it from the debug config option.

DocImpact

Change-Id: I298c40b71ed0b8772ff956f61f8d94217bce0e11
Merge "Turn off debug logging in sqlalchemy by default"