ubuntu-minimal.conf config fragment renamed to distribution.conf

Hi,

There's a couple of changes in the config fragments: * ubuntu-minimal.conf config fragment has been renamed to distribution.conf. distribution.conf contains the minimal configurations to be able to boot the supported distributions (Fedora, OpenEmbedded and Ubuntu). It isn't specific to Ubuntu baseline anymore. * ubuntu.conf has been removed. the config fragment isn't used anymore since a long time. Obviously, people prefer to use "minimal".

I've updated a few CI jobs. Please, make sure to update the builds affected by this change. Thanks.

Cheers, -- Fathi Boudra Builds and Baselines Manager | Release Manager Linaro.org | Open source software for ARM SoCs