Fix disable_deadlock_detect

Summary:
The initial port of innodb_deadlock_detect was completely broken.
Rather than disable deadlock detection, it just ignored the results of it.

This flaw was found and reported by: github.com/zhaiwx1987

It is unclear if this is still a useful feature, but this fixes it.

Test Plan: Jenkins

Reviewers: jtolmer

Reviewed By: jtolmer