[scripts/fast-reboot] stop timers in advance (sonic-net#2131)

- What I did
Service timers may trigger service start in the middle of warm-reboot. Stopping them in advance prevents this issue.

- How I did it
Stopped all service timers that are part of sonic-delayed.target

- How to verify it
Run warm-reboot.

Signed-off-by: Stepan Blyschak <stepanb@nvidia.com>

scripts/fast-reboot

@@ -599,6 +599,13 @@ if [ -x ${LOG_SSD_HEALTH} ]; then
     ${LOG_SSD_HEALTH}
 fi
 
+# Stop any timers to prevent any containers starting in the middle of the process.
+TIMERS=$(systemctl list-dependencies --plain sonic-delayed.target | sed 1d)
+for timer in ${TIMERS}; do
+    debug "Stopping ${timer} ..."
+    systemctl stop ${timer}
+    debug "Stopped ${timer} ..."
+done
 
 # Kill nat docker after saving the conntrack table
 debug "Stopping nat ..."