While the slave is busy, just accumulate master input.

Processing command from the master while the slave is in busy state is
not correct, however we cannot, also, just reply -BUSY to the
replication stream commands from the master. The correct solution is to
stop processing data from the master, but just accumulate the stream
into the buffers and resume the processing later.

Related to #5297.

src/server.c

@@ -2683,7 +2683,6 @@ int processCommand(client *c) {
 
     /* Lua script too slow? Only allow a limited number of commands. */
     if (server.lua_timedout &&
-          !(c->flags & CLIENT_MASTER) &&
           c->cmd->proc != authCommand &&
           c->cmd->proc != replconfCommand &&
         !(c->cmd->proc == shutdownCommand &&