Fix bug in handling schedules when `EndTime` < `StartTime` and are in different timezones

[AndreyNudko]

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It was possible to end up in a state when interval end is >24 hours before interval start (this is some quirk of the j.u.Calendar which I don't fully understand - but order of calls to setTimeZone() and setTimeInMillis() somehow matters). Adding 1 day in this case is not enough, since resulting interval is still inverted. This patch addresses the problem by moving end timestamp forward as long as it is behind the start.

Fixes #486