FIXME: Temporary: Use archive.ubuntu.com only

FIXME: Temporary: Use archive.ubuntu.com only

We recently removed blacklists for a few mirrors, on account
of upstream Fuel@OPNFV fixing mirror selection in [1].

Although the mechanism will be polished a little, it works very
nicely; pointing us to [2], where we seem to trigger some flood
protection at sync, leading to dropped connections and failed builds.

Keep using the official Ubuntu Archive mirror [3] until we sort this out.

Fixes: ARMBAND-136

[1] https://gerrit.opnfv.org/gerrit/#/c/22195
[2] http://mirrors.se.eu.kernel.org/ubuntu/
[3] http://archive.ubuntu.com/ubuntu/

Change-Id: If9247f829ee314d4c71dafa84b6cd13b384484f0
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>