Comment 6 for bug 91814

We had a similar upgrade issue with libc6. Currently there are two environment variables that may be interessting:
RELEASE_UPGRADE_IN_PROGRESS=1
RELEASE_UPGRADE_MODE={desktop,server}

The libc6.preinst looks like this:
...
                  db_subst glibc/upgrade services $services
                    if [ "$RELEASE_UPGRADE_MODE" = desktop ]; then
                        db_input medium glibc/upgrade || true
                    else
                        db_input critical glibc/upgrade || true
                    fi
...

We can probably use a similar solution. If the default is to restart, we need to be careful that nothing on the desktop breaks due to the restart.