automation: fix race condition in adl-suspend test

If system suspends too quickly, the message for the test controller to
wake up the system may be not sent to the console before suspending.
This will cause the test to timeout.

Fix this by calling sync on the console and waiting a bit after printing
the message. The test controller then resumes the system 30s after the
message, so as long as the delay + suspending takes less time it is
okay.

Signed-off-by: Marek Marczykowski-Górecki <marmarek@invisiblethingslab.com>
Release-acked-by: Henry Wang <Henry.Wang@arm.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>

automation/scripts/qubes-x86-64.sh

@@ -54,11 +54,12 @@ until grep 'domU started' /var/log/xen/console/guest-domU.log; do
     sleep 1
 done
 echo \"${wait_and_wakeup}\"
+# let the above message flow to console, then suspend
+sync /dev/stdout
+sleep 5
 set -x
 echo deep > /sys/power/mem_sleep
 echo mem > /sys/power/state
-# now wait for resume
-sleep 5
 xl list
 xl dmesg | grep 'Finishing wakeup from ACPI S3 state' || exit 1
 # check if domU is still alive