Pai master Label is missing on single node deployment

Organization Name:
Advantech

Short summary about the issue/question:
pai-master=true label is missing on single node deployment

Brief what process you are following:
We deployment one master and one worker on single node due to hardware resource limitation.
The deployment is OK when we comment some duplicate checking code. However, the deployment is pending upon openpai service deployment.
I check the node status and found that the pai-master is missing.
The deployment can be moved on when I restore the tag on demand( kubectl label nodes ${node} pai-master=true )
Where should I force the master label function upon single node deployment?

How to reproduce it:
1, Checkout openPAI v1.5.0, and set master and worker as same node on layout.yaml
2. Run quick-start-service.sh script

OpenPAI Environment:

• OpenPAI version:
  V1.5.0
• OS (e.g. from /etc/os-release):
  Ubuntu 18.04.3 LTS

Start with the v1.5.0 layout.yaml configuration and quick-start-service.sh reproduction steps, using a single node for both master and worker. Check where the deployment handles the pai-master label and compare it with the manual kubectl label command. Done means the label is applied automatically and the OpenPAI service deployment progresses without manual intervention.