Publication Date will be set to Null if the user other than entity owner changes the moderation state

Publication Date will be set to Null if the user other than entity owner changes the moderation state.

Steps to reproduce:

1. publish a node using one user role or uid
2. Edit the published node and save as draft using different user
3. The published at value will be set to PUBLICATION_DATE_DEFAULT
4. Once the draft gets published - it will take the current time as published date

Resolution:
The Published_at field value should not change irrespective of user editing the node.