Allow AUTH when Redis is busy because of timedout Lua script.

If the server is password protected we need to accept AUTH when there is
a server busy (-BUSY) condition, otherwise it will be impossible to send
SHUTDOWN NOSAVE or SCRIPT KILL.

This fixes issue #708.

src/redis.c

@@ -1667,6 +1667,7 @@ int processCommand(redisClient *c) {
 
     /* Lua script too slow? Only allow commands with REDIS_CMD_STALE flag. */
     if (server.lua_timedout &&
+          c->cmd->proc != authCommand &&
         !(c->cmd->proc == shutdownCommand &&
           c->argc == 2 &&
           tolower(((char*)c->argv[1]->ptr)[0]) == 'n') &&