Overlayfs needs to do an idmap mount of each layer and the cleanup
function just unmounts and deletes the directories. However, when the
resource is busy, the umount fails.
Let's make the unmount detached so the unmount will eventually be done
when it's not busy anymore. Also, making it detached solves the issues with
the unmount failing because it is busy.
Big kudos to @mbaynton for reporting this issue with lot of details,
nailing it down to containerd lines of code and showing all the log
lines to understand the big picture.
Fixes: #10704
Signed-off-by: Rodrigo Campos <rodrigoca@microsoft.com>
004f3951d5