Fixes and cleanup after implementation of the S3 and SSH roadmap

internal/adapters/ssh/hostkeys.go

@@ -54,6 +54,9 @@ func acceptNewHostKeyCallback(options Options) (cryptossh.HostKeyCallback, error
 				return fmt.Errorf("host key for %s has changed: %w", hostname, err)
 			}
 		}
+		if options.ReadOnlyKnownHosts {
+			return nil
+		}
 		if options.KnownHosts == "" {
 			return fmt.Errorf("host key for %s is unknown and no writable known_hosts path is available", hostname)
 		}