Bug#807456: mention how to abort, right there in the message

[積丹尼 Dan Jacobson]

Gasp, I finally found the culprits,

systemctl show \* -p TimeoutStopUSec -p Id|perl -e '
use strict;
use warnings FATAL => q(all);
my %h;
while (<>) {
    chomp;
    if ( !length ) {
        printf "%s|%s\n", @h{ q(TimeoutStopUSec), q(Id) };
        undef %h;
    }
    elsif (/(.*)=(.*)/) { $h{$1} = $2; }
    else                { die; }
}
'|sort -n

...
1min 30s|systemd-user-sessions.service
1min 30s|systemd-vconsole-setup.service
1min 30s|user at 1000.service
5min|dictd.service
5min|exim4.service
5min|nodm.service
5min|ntp.service
10min|mysql.service
30s|systemd-machine-id-commit.service
30s|systemd-random-seed.service
30s|systemd-rfkill.service

So much work to dig them out.