Risk calculation cannot be restarted after time travel (EXPOSUREAPP-6646) (#3327)

* Store Risk Result at current server time in case the device time is incorrect

* Fix RiskLevelTaskTest.kt

* Fix RiskLevelTaskTest.kt by not using hardcoded instant value

Co-authored-by: harambasicluka <64483219+harambasicluka@users.noreply.github.com>
Co-authored-by: Chilja Gossow <49635654+chiljamgossow@users.noreply.github.com>
Co-authored-by: AlexanderAlferov <64849422+AlexanderAlferov@users.noreply.github.com>