[fix] bug in schedule logic

[Menashe-zadara]

when a schedule is calculated the logic of Cron is described in the source:
/* the dom/dow situation is odd. '* * 1,15 * Sun' will run on the
* first and fifteenth AND every Sunday; '* * * * Sun' will run only
* on Sundays; '* * 1,15 * *' will run only the 1st and 15th. this
* is why we keep 'e->dow_star' and 'e->dom_star'. yes, it's bizarre.
* like many bizarre things, it's the standard.
*/

meaning the logic between day of month and day of week should be OR.

Actual behavior

the schedule calculates the next date which complies with DOW AND DOM ( '* * 15 * 1' will find next date which is a Sunday and the 15th of the month, instead of the next Sunday OR the next 15th of the month)

Expected behavior

find next date which complies either with DOM OR with DOW