Kolla images for ussuri and train

As you may know we have a job on Linaro CI to build Kolla images. Normally it does LDC (Linaro Developer Cloud) ones and also not-modified upstream ones.

Some time ago I merged CI jobs upstream for it. So "kolla/debian-source-*" images exist with "train-aarch64" tag for stable/train branch and "master-aarch64" for master one.

Please migrate to use those upstream ones instead of "linaro/debian-source-*" ones (tagged "train-XYZ" and "ussuri-XYZ").

Building of Kolla images in "linaro" namespace will be limited to images used by Linaro Developer Cloud as those ones may contain Linaro specific changes or patches.