fix no newline when returning JSON format(#2676)

[Egor-OSSRevival]

What type of PR is this?

• bug
• feature
• enhancement

What problem(s) does this PR solve?

Issue(s) number: #2676

Description:

There seems to be no newline when returning JSON format with curl request

How do you solve it?

Add newline after json returns

Special notes for your reviewer, ex. impact of this fix, design document, etc:

Before:

After:

Checklist:

Tests:

• Unit test(positive and negative cases)
• Function test
• Performance test
• N/A

Affects:

• Documentation affected (Please add the label if documentation needs to be modified.)
• Incompatibility (If it breaks the compatibility, please describe it and add the label.）
• If it's needed to cherry-pick (If cherry-pick to some branches is required, please label the destination version(s).)
• Performance impacted: Consumes more CPU/Memory

Release notes:

Please confirm whether to be reflected in release notes and how to describe:
Fixed the bug no newline when returning JSON format with curl request

[CLAassistant]

All committers have signed the CLA.

[Egor-OSSRevival]

@monadbobo @dutor @lilydjwg Can someone review?