folder_block_manager_test: test incremental reclamation
folder_block_manager_test: test incremental reclamation

Issue: KBFS-749

keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/client,keybase/client,keybase/client,keybase/client,keybase/client,keybase/kbfs,keybase/client,keybase/kbfs,keybase/client