install/56384: Exiting and restarting sysinst during installation leaves /targetroot unmounted

[logix%foobar.franken.de@localhost]

>Number:         56384
>Category:       install
>Synopsis:       Exiting and restarting sysinst during installation leaves /targetroot unmounted
>Confidential:   no
>Severity:       non-critical
>Priority:       low
>Responsible:    install-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed Sep 01 10:30:00 +0000 2021
>Originator:     Harold Gutch
>Release:        9.99.88
>Organization:
>Environment:
NetBSD  9.99.98 NetBSD 9.99.98 (GENERIC) #0: Thu Aug 19 12:13:37 UTC 2021  mkrepro%mkrepro.NetBSD.org@localhost:/usr/src/sys/arch/amd64/compile/GENERIC amd64
>Description:
Selecting "x: Exit sysinstall" in sysinst unmounts /targeroot .  Running sysinst again then doesn't mount /targetroot and doing anything in the "Utility menu" or the "Config menu" that wants to write to a file (like network configuration, changing the root password, adding a user, ...) will fail.
>How-To-Repeat:
1) go through a normal installation (boot install medium etc.)
2) at the end, select "x: Exit sysinstall"
3) at the shell prompt, run "sysinst" again
4) go to "f: Config menu" and select (for example) "o: Add a user"
5) Observe "Command failed" as it tries to mkdir /home/$USERNAME
>Fix:
As /targetroot will be umounted properly anyway once the system reboots, can the umounting dance in cleanup() in sysinsts's main.c perhaps be removed?  Not sure if that has unwanted side effects...