Handle multiple process_waits_in checks identically to a single check

[mmiikkkkaa]

The process_waits_in method exists in two overloaded variantes: with a single activityId and with multiple activityIds.

The current implementation of the multiple activityIds variant causes problems due to not finding the "job", while the single activityId variant works. The multiple activityId variant might use the same operation as the single activityId variant, this would eliminiate the problems.

BTW: Since the multiple activityIds uses varargs it automatically covers the single activityId variant. Therefore the single variant can be removed completely.