Bootstrapping cannot be cancelled once image copying has started

[Jeff Pihach]

It's not possible to cancel a bootstrap once it starts to download the images. After the download completes it continues on bootstrapping.

juju bootstrap lxd lxd
Creating Juju controller "lxd" on lxd/localhost
Looking for packaged Juju agent binaries
Starting new instance for initial controller
Launching instance
^CInterrupt signalled: waiting for bootstrap to exitmages.ubuntu.com/releases/: 28%
^CInterrupt signalled: waiting for bootstrap to exitmages.ubuntu.com/releases/: 30%
^CInterrupt signalled: waiting for bootstrap to exit
^CInterrupt signalled: waiting for bootstrap to exit
^CInterrupt signalled: waiting for bootstrap to exit
^CInterrupt signalled: waiting for bootstrap to exitmages.ubuntu.com/releases/: 36%
^CInterrupt signalled: waiting for bootstrap to exit
copying image for ubuntu-xenial from https://cloud-images.ubuntu.com/releases/: 89%

[Anastasia (anastasia-macmood)]

Removing 2.1 milestone as we will not be addressing this issue in 2.1.