Misc updates to get it to work on debian

Force Ec2 being the only datasource used. Otherwise it will try a different IP
and wait 120s to timeout. Also reduce the timeouts a bit.

Use our mirrors.

No need to use the debconf-set anymore as we're adding the config in the
cloud.cfg file. Also no need to remove exim as its the distro default. No need
to rerun update-initramfs as apt already does that for us.

Remove the debian specific cloud.cfg.d file which pulls in another datasource.

Remove unused files