TEST-80: synchronize explicitly instead of by time

This removes "sleep" invocations, and makes the notify access testcase a
lot more robust to runtime jitter. We use a pair of fifos in the fs to
sync instead.

Also various other improvoements, including comments.

(Also removes the unnecessary "no-qemu" restriction)

test/units/testsuite-80.sh

@@ -9,17 +9,35 @@ set -o pipefail
 
 : >/failed
 
+mkfifo /tmp/syncfifo1 /tmp/syncfifo2
+
+sync_in() {
+    read -r x < /tmp/syncfifo1
+    test "$x" = "$1"
+}
+
+sync_out() {
+    echo "$1" > /tmp/syncfifo2
+}
+
+export SYSTEMD_LOG_LEVEL=debug
+
 systemctl --no-block start notify.service
-sleep 2
+
+sync_in a
 
-assert_eq "$(systemctl show notify.service -p StatusText --value)" "Test starts, waiting for 5 seconds"
 assert_eq "$(systemctl show notify.service -p NotifyAccess --value)" "all"
-sleep 5
+assert_eq "$(systemctl show notify.service -p StatusText --value)" "Test starts"
+
+sync_out b
+sync_in c
 
 assert_eq "$(systemctl show notify.service -p NotifyAccess --value)" "main"
-assert_eq "$(systemctl show notify.service -p StatusText --value)" "Sending READY=1 in an unpriviledged process"
+assert_eq "$(systemctl show notify.service -p StatusText --value)" "Sending READY=1 in an unprivileged process"
 assert_rc 3 systemctl --quiet is-active notify.service
-sleep 10
+
+sync_out d
+sync_in e
 
 systemctl --quiet is-active notify.service
 assert_eq "$(systemctl show notify.service -p StatusText --value)" "OK"
@@ -28,5 +46,7 @@ assert_eq "$(systemctl show notify.service -p NotifyAccess --value)" "none"
 systemctl stop notify.service
 assert_eq "$(systemctl show notify.service -p NotifyAccess --value)" "all"
 
+rm /tmp/syncfifo1 /tmp/syncfifo2
+
 touch /testok
 rm /failed