The build now happens in a loop and the monitor is run after every
build. The monitor can return `ErrReload` to signal to the main thread
that it should reload the build result.
This will be used in the future to move the monitor into a callback
rather than as a separate existence. It allows the monitor to not
control the build itself which now makes it possible to completely
remove the controller.
Signed-off-by: Jonathan A. Sternberg <jonathan.sternberg@docker.com>
Tonis Tiigi