The `--update-parallelism` flaag should default to 0, which is
interpreted by the backend as unlimited. In other words, by default all
services should update simultaneously.
Signed-off-by: Arnaud Porterie (icecrime) <arnaud.porterie@docker.com>
Upstream-commit: f22d0174f33e084445c5845c95aca346e187fb02
Component: engine