Implemented getNextMount for ArchiveForRepack mounts.

common/dataStructures/MountType.cpp

common/dataStructures/MountType.hpp

objectstore/ArchiveQueueAlgorithms.hpp

objectstore/ArchiveQueueToTransferAlgorithms.cpp

objectstore/ArchiveQueueToTransferForRepackAlgorithms.cpp

scheduler/OStoreDB/OStoreDB.cpp

scheduler/OStoreDB/OStoreDB.hpp

scheduler/OStoreDB/OStoreDBTest.cpp

scheduler/Scheduler.cpp

scheduler/SchedulerDatabase.hpp

scheduler/SchedulerDatabaseTest.cpp