nfs/Connection: use only BroadcastError()

Since BroadcastError() calls BroadcastMountError(), there's no need to
check mount_finished here.

src/lib/nfs/Connection.cxx

@@ -299,10 +299,7 @@ NfsConnection::OnSocketReady(unsigned flags)
 		DestroyContext();
 		closed = true;
 
-		if (!mount_finished)
-			BroadcastMountError(std::move(error));
-		else
-			BroadcastError(std::move(error));
+		BroadcastError(std::move(error));
 	}
 
 	assert(in_event);