While #6204 addressed the stopped state for handling signals in the main
process, it did not update exec processes in the same way. This change
mirrors that adjustment for exec processes.
Getting state of a stopped container would fail and could lead containerd
to not detecting that the container had actually stopped. Now stopped and
deleted containers return `stopped` state.
Also makes other messages more consistent when container is stopped. Some
where still sending messages to runsc and failing in different ways. Now
they go through `initState` state machine like the other messages.
There are a few changes to improve debugability with it as well.
Fixes#5861
PiperOrigin-RevId: 380698513
gvisor-containerd-shim is not compatible with containerd 1.1 or earlier.
Starting from containerd 1.2, shim v2 is the preferred interface.
PiperOrigin-RevId: 351485556
Noah Fontes
Fabricio Voznika