folder_branch_ops: partial sync config with no paths == disabled
folder_branch_ops: partial sync config with no paths == disabled

When a partial sync config comes in with no paths, disable syncing on
the TLF instead -- that way it won't show up in `keybase fs sync show`
anymore.

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