Properly detect InnoDB setups which are "NO" or "DISABLED"

Summary: See D2160, http://dev.mysql.com/doc/refman/5.5/en/show-engines.html

Test Plan: Ran setup.

Reviewers: vrana, btrahan

Reviewed By: vrana

CC: aran

Differential Revision: https://secure.phabricator.com/D2219