Detect missing InnoDB in MySQL

Summary: See T993. MySQL fails very very softly if you request an engine which does not exist. Detect and fail if the InnoDB engine is missing or broken.

Test Plan: Faked InnoDB missing, got a failure. Ran normally, got success.

Reviewers: btrahan, vrana, jungejason

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T993

Differential Revision: https://secure.phabricator.com/D2160