[CDAP-20815] Fix pipeline description on pipeline upgrade

[vsethi09]

Issue

CDAP-20815 Pipeline’s description is replaced with “Data Pipeline Application” when invoking /upgrade REST API

Repro Steps

To reproduce the issue:

• Deploy a pipeline in an instance with some description.
• Either follow the pipeline upgrade process or call the POST /upgrade method for the pipeline.
• Once upgrade finishes, check pipeline description. It’s been set to “Data Pipeline Application”

This can be reproed in 6.6.0 - 6.9.x. May also be reproduced in versions < 6.6.0.

Root Cause

On pipeline upgrade the description of the pipeline is preserved and set to null. The null description is defaulted to Data Pipeline Application (code)

Solution

Preserve the pipeline description during upgrades for both Batch and Stream pipelines.

Verification

• Verified using sandbox instance.
• Created a pipeline with some description.
• Upgraded the pipeline.
• Verified that the description is the same and not changed to the default one.