[MRM-1294] start the search period from the *start* of the previous scan rather than the end to discover anything added in the middle. Some artifacts may get scanned twice, but this is a better consequence than not at all
archiva/trunk/archiva-modules/archiva-scheduled/src/main/java/org/apache/maven/archiva/scheduled/executors/ArchivaRepositoryScanningTaskExecutor.java