CompactionTool should close the store it uses for compacting files, in order to properly archive compacted files.

While using CompactionTool to offload RSes, noticed compacted files were never archived from original region dir, causing the space used by the region to actually double. Going through its compaction related code on HStore, which is used by CompactionTool for performing compactions, found out what that compacted files archiving happens mainly while closing the HStore instance. CompactionTool is never explicitly closing its HStore instance, so adding a simple patch that properly close the store.