Also wrap access in mutex.
Makes sure we don't have any pontential for races in accessing this.
It also doesn't really need to be/shouldn't be in the config.json anyway
Docker-DCO-1.1-Signed-off-by: Brian Goff <bgoff@cpuguy83-mbp.home> (github: cpuguy83)
Upstream-commit: c5e728c953e29b8008cdfb8367910e33ba28b99c
Component: engine