CI: heavily rework the container creation

Now everybody gets to rebuild their own containers if there is a change
(too old or change in the packages). This should allow the MR touching
the package list to succeed.

Removal of the container_check stage, we can just have this in a
before_script.

Removal of the manual creation of the containers, not needed as we better
just increment <DISTRO>_TAG.

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@gmail.com>