[Bug] [dolphinscheduler-api] Set timing scheduler through API

[boy-xiaozhang]

Search before asking

• I had searched in the issues and found no similar issues.

What happened

The scenario is as follows:
The user uses the API interface to set the timing scheduling processInstancePriority as an optional parameter, but there is no default value, which causes the Scheduler to fail to execute and throws an exception

What you expected to happen

The default processInstancePriority should be added to ensure that the user sets the timing scheduling task through the API is correct

How to reproduce

The process of reproducing the BUG is as follows

curl -X POST "http://127.0.0.1:12345/dolphinscheduler/projects/%E5%BA%94%E7%94%A8%E8%B0%83%E5%BA%A6/schedule/create" -H "Request-Origion:SwaggerBootstrapUi" -H "accept:/" -H "Content-Type:application/x-www-form-urlencoded;charset=UTF-8" -d "processDefinitionId=6264" -d "schedule={'startTime':'2019-06-10 00:00:00','endTime':'2019-06-13 00:00:00','crontab':'0 0 3/6 * * ? *'}"

Anything else

No response

Are you willing to submit PR?

• Yes I am willing to submit a PR!

Code of Conduct

• I agree to follow this project's Code of Conduct

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