update fuelmenu to write to /etc/fuel/astute.yaml

[Matthew Mosesohn]

In order to provide docker containerization and sharing of system files, we need to put all the config files into a subdir of /etc so it can be shared easily. There are some LXC limitations on sharing single files, while directories work much better.

There is a workaround in place to symlink /etc/astute.yaml to /etc/fuel/astute.yaml, but it's not very clean.