A lot of flags have been added on the output of `docker help`. Use a
more robust method to extract the list of available subcommands by
spotting the `Command:` line and the next blank line.
Signed-off-by: Vincent Bernat <vincent@bernat.im>
Upstream-commit: 34fe2a372576907cb7ec26cf22ac4e93b8974f6e
Component: engine