Current status for /etc/mtab

[William Harrington]

/etc/mtab is no longer being referenced in util-linux-2.27.1, systemd 228, and future glibc releases.

So far it has been appropriate to have /etc/mtab as a link to /proc/self/mounts.

We should be able to remove the creation of mtab altogether in the future.

Refer to the following for more information:

​https://github.com/systemd/systemd/issues/1495 ​https://sourceware.org/bugzilla/show_bug.cgi?id=19108 ​https://sourceware.org/ml/libc-alpha/2015-11/msg00418.html ​https://github.com/karelzak/util-linux/commit/02501746 ​https://github.com/systemd/systemd/blob/v228/NEWS ​https://github.com/systemd/systemd/blob/v228/README