Comment 3 for bug 2059195

I was able to reproduce this with 22.04, snapd 2.61.1. This is what is reported by findmnt:

```
maciek@vm:~$ findmnt
TARGET SOURCE FSTYPE OPTIONS
/ /dev/vda2 ext4 rw,relatime,errors=remount-ro
├─/sys sysfs sysfs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/kernel/security securityfs securityfs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/fs/cgroup cgroup2 cgroup2 rw,nosuid,nodev,noexec,relatime,nsdelegate,memory_recursiveprot
│ ├─/sys/fs/pstore pstore pstore rw,nosuid,nodev,noexec,relatime
│ ├─/sys/firmware/efi/efivars efivarfs efivarfs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/fs/bpf bpf bpf rw,nosuid,nodev,noexec,relatime,mode=700
│ ├─/sys/kernel/debug debugfs debugfs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/kernel/tracing tracefs tracefs rw,nosuid,nodev,noexec,relatime
│ ├─/sys/fs/fuse/connections fusectl fusectl rw,nosuid,nodev,noexec,relatime
│ └─/sys/kernel/config configfs configfs rw,nosuid,nodev,noexec,relatime
├─/proc proc proc rw,nosuid,nodev,noexec,relatime
│ └─/proc/sys/fs/binfmt_misc systemd-1 autofs rw,relatime,fd=29,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=41325
│ └─/proc/sys/fs/binfmt_misc binfmt_misc binfmt_misc rw,nosuid,nodev,noexec,relatime
├─/dev udev devtmpfs rw,nosuid,relatime,size=1949512k,nr_inodes=487378,mode=755,inode64
│ ├─/dev/pts devpts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000
│ ├─/dev/shm tmpfs tmpfs rw,nosuid,nodev,inode64
│ ├─/dev/hugepages hugetlbfs hugetlbfs rw,relatime,pagesize=2M
│ └─/dev/mqueue mqueue mqueue rw,nosuid,nodev,noexec,relatime
├─/run tmpfs tmpfs rw,nosuid,nodev,noexec,relatime,size=397560k,mode=755,inode64
│ ├─/run/lock tmpfs tmpfs rw,nosuid,nodev,noexec,relatime,size=5120k,inode64
│ ├─/run/credentials/systemd-sysusers.service ramfs ramfs ro,nosuid,nodev,noexec,relatime,mode=700
│ ├─/run/snapd/ns tmpfs[/snapd/ns] tmpfs rw,nosuid,nodev,noexec,relatime,size=397560k,mode=755,inode64
│ │ ├─/run/snapd/ns/firefox.mnt nsfs[mnt:[4026532961]] nsfs rw
│ │ ├─/run/snapd/ns/snap-store.mnt nsfs[mnt:[4026532962]] nsfs rw
│ │ └─/run/snapd/ns/snapd-desktop-integration.mnt nsfs[mnt:[4026532964]] nsfs rw
│ └─/run/user/1000 tmpfs tmpfs rw,nosuid,nodev,relatime,size=397556k,nr_inodes=99389,mode=700,uid=1000,gid=1000,inode64
│ ├─/run/user/1000/gvfs gvfsd-fuse fuse.gvfsd-fuse rw,nosuid,nodev,relatime,user_id=1000,group_id=1000
│ └─/run/user/1000/doc portal fuse.portal rw,nosuid,nodev,relatime,user_id=1000,group_id=1000
├─/snap/bare/5 /dev/loop0 squashfs ro,nodev,relatime,errors=continue,threads=single
├─/snap/core22/1122 /dev/loop1 squashfs ro,nodev,relatime,errors=continue,threads=single
├─/snap/firefox/3836 /dev/loop2 squashfs ro,nodev,relatime,errors=continue,threads=single
├─/snap/gnome-42-2204/141 /dev/loop3 squashfs ro,nodev,relatime,errors=continue,threads=single
├─/snap/gtk-common-themes/1535 /dev/loop4 squashfs ro,nodev,relatime,errors=continue,threads=single
├─/snap/snap-store/959 /dev/loop5 squashfs ro,nodev,relatime,errors=continue,threads=single
├─/snap/snapd/20671 /dev/loop6 squashfs ro,nodev,relatime,errors=continue,threads=single
├─/snap/snapd-desktop-integration/83 /dev/loop7 squashfs ro,nodev,relatime,errors=continue,threads=single
├─/boot/efi /dev/vda1 vfat rw,relatime,fmask=0077,dmask=0077,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro
└─/var/snap/firefox/common/host-hunspell /dev/vda2[/usr/share/hunspell] ext4 ro,noexec,noatime,errors=remount-ro
```

AFAICT the mount is a result of this plug:

```
  host-hunspell:
    interface: mount-control
    mount:
    - what: /usr/share/hunspell
      where: $SNAP_COMMON/host-hunspell
      persistent: true
      options:
      - ro
      - bind
      - noatime
      - noexec
```

and this interface hook:

```
maciek@vm:~$ grep -n '' /snap/firefox/current/snap/hooks/connect-plug-host-hunspell
1:#!/bin/sh
2:
3:mkdir -p $SNAP_COMMON/host-hunspell
4:snapctl mount --persistent -o ro,bind,noatime,noexec /usr/share/hunspell $SNAP_COMMON/host-hunspell
```