tests: add basic validation of running services

For determinist test results lvm2/dm service shall not be present
and running in the system as it may randomize test results.

In case they are found present, this test ends with warning (not failure).

test/shell/000-basic.sh

@@ -34,3 +34,15 @@ get_devs
 # ensure we do not crash on a bug in config file
 aux lvmconf 'log/prefix = 1""'
 not lvs "${DEVICES[@]}"
+
+# validate testing machine with its services is in expected state and will not interfere with tests
+if systemctl -a >out 2>/dev/null ; then
+	for i in dm-event lvm2-lvmpolld lvm2-monitor ; do
+	echo $i
+		grep $i out | not grep -v masked || {
+			cat out
+			should not echo "Present unmasked $i service/socket may randomize testing results!"
+			echo "+++++ Stop & Mask with systemctl +++++"
+		}
+	done
+fi