* tests/av-store: use future::join instead of future::select
* tests/backing: use future::join instead of future::select
* tests/provisioner: use future::join instead of future::select
* tests/av-dist: use future::join instead of future::select
* tests/av-recovery: use future::join instead of future::select
* tests/bridge: use future::join instead of future::select
* tests/collator-protocol: use future::join instead of future::select
* tests/stmt-dist: use future::join instead of future::select
* fix tests