Automatic reconnect ignores settings applied for the connection

`Client::Impl::RetryGuard` performs automatic connection resets so the application code doesn't have a chance to restore expected connection settings applied before executing the current request.

For example, `SET mutations_sync=2`, automatic reconnect, `ALTER TABLE` sequence causes mutations to be executed asynchronously when the application assumes synchronous execution of the mutation.

It looks like connection settings should be stored in the Client::Impl and they should be re-applied in case of such reconnect before executing the client query.