Comment 1 for bug 1607920

Personally I think we should modify MNTTAB in zfs-linux to point to /proc/self/mounts. This may not be completely straightforward *(there are a number of places that point to /etc/mnttab directly, or have logic around it and /proc/mounts), but it should be doable. I like this solution most because it doesn't require us to increase the number of dependencies in the zfs systemd scripts.