[TechDebt] Race condition

[ndeloof]

Description

ContainerState hold a list of discovered/created containers. As we run the convergence process in parallel on multiple containers, we noticed race conditions accessing this centralized status, as the internal list get updated while concurrent access is missing data.

I suggest we cleanup this code by making convergence a dedicated struct, passing required container operations as an interface (so we can write more unit tests). Convergence would then hold the actual container set, and manage concurrent access accordingly.

[ndeloof]

internally tracked as https://docker.atlassian.net/browse/IL-271