be more explicit tha the reboots are due to upgrades

This will be more useful to users than the internals of the procedure.

howto/upgrades/bullseye.md

@@ -75,7 +75,7 @@ See the "conflicts resolution" section below for how to handle
 
         systemctl disable modules_disabled.timer &&
         puppet agent --disable "running major upgrade" &&
-        shutdown -r +1 "rebooting with module loading enabled"
+        shutdown -r +1 "bullseye upgrade step 3: rebooting with module loading enabled"
 
         export LC_ALL=C.UTF-8 &&
         sudo ttyrec -a -e screen /var/log/upgrade-bullseye.ttyrec
@@ -135,7 +135,7 @@ See the "conflicts resolution" section below for how to handle
         /usr/local/sbin/clean_conflicts &&
         systemctl start apt-daily.timer &&
         printf "End of Step 7\a\n" &&
-        shutdown -r +1 "rebooting to get rid of old kernel image..."
+        shutdown -r +1 "bullseye upgrade step 7: removing old kernel image"
 
  8. Post-upgrade checks:
 
@@ -158,7 +158,7 @@ See the "conflicts resolution" section below for how to handle
         # reenable logins
         rm /etc/nologin
         printf "End of Step 8\a\n"
-        shutdown -r +1 "testing reboots one final time"
+        shutdown -r +1 "bullseye upgrade step 8: testing reboots one final time"
 
 [this guide to free up space]: http://www.debian.org/releases/buster/amd64/release-notes/ch-upgrading.en.html#sufficient-space