Dtest fails if it sees an unknown errors in the logs. This series
reduces severity of some errors (since they are actually expected during
shutdown) and removes some others that duplicate already existing errors
that dtest knows how to deal with. Also fix one case of unhandled
exception in schema management code.
* 'dtest-fixes-v1' of github.com:gleb-cloudius/scylla:
raft: getting abort_requested_exception exception from a sm::apply is not a critical error
schema_registry: fix abandoned feature warning
service: raft: silence rpc::closed_errors in raft_rpc
b52429f724