Correct the timespec fields for the timer trigger

The parser rework for the new seeded PRNG jitter implementation in
change Idd9d3a8cfa791860e46e4fc508566417f5d5a9bf omitted the month
field and shifted the hour and day field by one. Correct this so
that the timer triggers continue to be parsed the same as before
that change.

Change-Id: If7988e28bd1e8fed7e21f2deb6eef9b51c8c2ae3

zuul/driver/timer/__init__.py

@@ -124,8 +124,9 @@ class TimerDriver(Driver, TriggerInterface):
                     try:
                         cron_args = dict(
                             minute=parts[0],
-                            hour=parts[2],
-                            day=parts[3],
+                            hour=parts[1],
+                            day=parts[2],
+                            month=parts[3],
                             day_of_week=parts[4],
                             second=None,
                         )