Adds a mutex to protect the status, as well. When running the race
detector with the unit test, we can see that the Status field is written
without holding this lock. Adding a mutex to read and set status
addresses the issue.
Signed-off-by: Stephen J Day <stephen.day@docker.com>
Upstream-commit: 7db30ab0cdf072956d2ceda833b7de22fe17655c
Component: engine