Warnings when running mars on ray container

**Describe the bug**
There is a lot of warning when running mars on ray container with python 3.7.7

**To Reproduce**
1. Your Python version

python 3.7.7 in the ray docker.
The docker is created with the cmd below:
`docker run -it --shm-size=4.65gb -v /home/yizhengjiao/ray:/home/ray/ray --rm rayproject/ray:1.9.0`

2. The version of Mars you use
pymars-0.8.1

mars is installed with `pip install pymars`

3. Versions of crucial packages, such as numpy, scipy and pandas

Other packages are install with:
`pip install xgboost`
`pip install "xgboost_ray"`
`pip install lightgbm`

4. Full stack of the error.

base) ray@803dc5f4489d:~/ray/mars$ python boston_xgb.py
Web service started at http://0.0.0.0:41970
100%|██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 100.0/100 [00:00<00:00, 584.26it/s]
100%|██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 100.0/100 [00:00<00:00, 803.99it/s]
100%|██████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 100.0/100 [00:00<00:00, 387.23it/s]
0%| | 0/100 [00:00

Reproduce boston_xgb.py in the rayproject/ray:1.9.0 container with Python 3.7.7, then trace the shared_memory/resource_tracker warnings shown in the output. The issue does not define whether done means eliminating the warnings or documenting them as harmless, so that outcome needs clarification before implementation.

Written by the indexing model from the issue text.