Update of Export Task shall update the device name and reset the status to TO_SCHEDULE

[gunterze]

Otherwise already completed task will not be rescheduled on receive of an additional object of the entity to export.

Updating the device name facilitate fall-over installations, where the device on which the export task was initiated - on receive of the first object of the entity - may have got down, and the export task get updated by another device, to which an upfront load balancer switched the traffic after the failure of the primary device.