Description of problem:

systemd allows mountpoints to be specified using unit files, eg:

-----------------
$ cat /usr/lib/systemd/system/proc-sys-fs-binfmt_misc.mount 
#  This file is part of systemd.
#
#  systemd is free software; you can redistribute it and/or modify it
#  under the terms of the GNU Lesser General Public License as published by
#  the Free Software Foundation; either version 2.1 of the License, or
#  (at your option) any later version.

[Unit]
Description=Arbitrary Executable File Formats File System
Documentation=https://www.kernel.org/doc/Documentation/binfmt_misc.txt
Documentation=http://www.freedesktop.org/wiki/Software/systemd/APIFileSystems
DefaultDependencies=no

[Mount]
What=binfmt_misc
Where=/proc/sys/fs/binfmt_misc
Type=binfmt_misc
-----------------

Although currently these are confined just to "built in" mountpoints
such as the proc filesystem in the example above, they could in
theory be used for real filesystems.

Currently libguestfs only looks at /etc/fstab to find mountpoints
so it would miss these.

Version-Release number of selected component (if applicable):

libguestfs 1.27.19