setup warning for mysql with default boolean syntax

Summary: Ref: T6747 add a setup warning if mysql is configured with the default boolean syntax

Test Plan: Run setup checks with default mysql config and then add the desired config option, restart and check again.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: epriestley

Maniphest Tasks: T6747

Differential Revision: https://secure.phabricator.com/D11030