IoTDB system load is too large to create timeseries

**To reproduce**
- set 1GB JVM memory (memory for schema is 100MB) and create 300,000 timeseries
- reboot the IoTDB server 

Then we can see we cannot create more timeseries since it's supposed to be allowed. 

The maximum number of timeseries should be 100,000,000 / 300 = 333,333.