Add support for changing basicBindDirs, basicEmptyDirs, basicSymlinks and basicBlacklist from /etc/oz/oz.conf

[xmikos]

Hello,

I am trying to make OZ sandbox work on Arch Linux, but it is not possible without heavy patching of oz-init/rootfs.go, especially basicBindDirs, basicEmptyDirs, basicSymlinks and basicBlacklist. This is because Arch Linux uses more modern filesystem layout (/bin, /sbin and /usr/sbin are symlinks to /usr/bin, /lib, /lib64 and /usr/lib64 are symlinks to /usr/lib, /run/media/$USER mountpoint directory is used instead of /media, etc.). I think Fedora and some other distributions also uses this new filesystem layout.

It would be great if you can make these basic lists and users /media directory mountpoint (which is also used elsewhere) configurable at runtime from /etc/oz/oz.conf.

[xSmurf]

If you submit a pull request, I'll consider it.