isodevice unable to unmount when using loopback

[Kev Bowring]

Using these stanzas to boot various iso's. Find that in bionic isodevice remains mounted (and if I try to manually do so - the device tells me it's busy)

Tested 17.10,17.04,16.04 - all work as expected.

menuentry "Xubuntu 18.04 Daily ISO" {
        set isofile="/boot/grubiso/bionic-desktop-amd64.iso"
        # or set isofile="/<username>/Downloads/ubuntu-12.04.2-desktop-amd64.iso"
        # if you use a single partition for your $HOME
        loopback loop (hd0,6)$isofile
        linux (loop)/casper/vmlinuz.efi boot=casper toram maybe-ubiquity iso-scan/filename=$isofile noprompt noswap noeject
        initrd (loop)/casper/initrd.lz
}

menuentry "Xubuntu Xenial" {
        set isofile="/boot/grubiso/xenial-desktop-amd64.iso"
        # or set isofile="/<username>/Downloads/ubuntu-12.04.2-desktop-amd64.iso"
        # if you use a single partition for your $HOME
        loopback loop (hd0,6)$isofile
        linux (loop)/casper/vmlinuz.efi boot=casper toram maybe-ubiquity iso-scan/filename=$isofile noprompt noswap noeject
        initrd (loop)/casper/initrd.lz
}

menuentry "Xubuntu Zesty" {
        set isofile="/boot/grubiso/zesty-desktop-amd64.iso"
        # or set isofile="/<username>/Downloads/ubuntu-12.04.2-desktop-amd64.iso"
        # if you use a single partition for your $HOME
        loopback loop (hd0,6)$isofile
        linux (loop)/casper/vmlinuz.efi boot=casper toram maybe-ubiquity iso-scan/filename=$isofile noprompt noswap noeject
        initrd (loop)/casper/initrd.lz
}

menuentry "Xubuntu Artful" {
        set isofile="/boot/grubiso/artful-desktop-amd64.iso"
        # or set isofile="/<username>/Downloads/ubuntu-12.04.2-desktop-amd64.iso"
        # if you use a single partition for your $HOME
        loopback loop (hd0,6)$isofile
        linux (loop)/casper/vmlinuz.efi boot=casper toram maybe-ubiquity iso-scan/filename=$isofile noprompt noswap noeject
        initrd (loop)/casper/initrd.lz
}

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 4.13.0-17.20-generic 4.13.8
Uname: Linux 4.13.0-17-generic x86_64
ApportVersion: 2.20.8-0ubuntu2
Architecture: amd64
CurrentDesktop: XFCE
Date: Sat Nov 25 09:17:23 2017
InstallationDate: Installed on 2017-09-02 (84 days ago)
InstallationMedia: Xubuntu 17.10 "Artful Aardvark" - Alpha amd64 (20170902)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Arbiel Perlacremaz (arbiel-perlacremaz)]

This bug affects previous Ubuntu releases. To circumvent this issue, choose "Try Ubuntu", add a terminal and unmount /isodevice
sudo umount -lfd /isodevice

[Arbiel Perlacremaz (arbiel-perlacremaz)]

In my previous post, change "add a terminal" by "open a terminal"