folder_branch_ops: always wait for archives on Shutdown
folder_branch_ops: always wait for archives on Shutdown

Operations that create temporary configs, like git, should wait for
all their unref'd blocks to be archived.  Otherwise, any unref'd
blocks will count towards the user's quota until garbage collection
kicks in two weeks later.  This is especially bad when deleting data
from a deleted repo.  (This is just a guess at the root cause for
keybase/keybase-issues#3342.)

Issue: keybase/keybase-issues#3342

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