docker: using opensuse leap instead of alpine
docker: using opensuse leap instead of alpine

Funnily enough, by doing so I've cut the image's size by half. Apparently
alpine has a very slim base image, but once you start adding packages,
opensuse ends up doing a *much* better job.

Signed-off-by: Miquel Sabaté Solà <b4d70704b9e7df580cab34510621dbd0aacb2dfd@suse.com>

mssola/todo,mssola/todo,mssola/todo,mssola/todo