[LINKIS #5043] Only start the eureka service if DISCOVERY is EUREKA

[wForget]

What is the purpose of the change

Only start the eureka service if DISCOVERY is EUREKA.

Related issues/PRs

Related issues: close #5043

Brief change log

Checklist

• I have read the Contributing Guidelines on pull requests.
• I have explained the need for this PR and the problem it solves
• I have explained the changes or the new features added to this PR
• I have added tests corresponding to this change
• I have updated the documentation to reflect this change
• I have verified that this change is backward compatible (If not, please discuss on the Linkis mailing list first)
• If this is a code change: I have written unit tests to fully verify the new behavior.

[peacewong]

LGTM.