mirror/ubuntu: use aptly instead of custom scripts

Currently, we are building ubuntu mirror by 'multistrap', then
mkrepo.sh which copying .deb from /var/cache/, downloading
other .deb and .udeb and creating local mirror.

First point is multistrap is not available on RHEL, SUSE, etc.
Second point is building chroot, configuring pkgs, directly
downloading packages is slow and we can't maintenance this bullshit.

Now we will use one docker container, run 'aptly' inside, do mirror all
.udeb and .deb from requirements-deb.txt and pushing it to local_mirror/

blueprint build-iso-on-fedora
Signed-off-by: Igor Gnatenko <ignatenko@mirantis.com>

Change-Id: Ieb23c70f31633f651abc1f8700e039700dca669c