Steps to reproduce:

1. Create a freestyle job with parameters
2. Add a credentials parameter and set a default credentials
3. Trigger the build

Expected: isDefaultValue = true
Actual isDefaultValue = false

The problem is here:
https://github.com/jenkinsci/credentials-plugin/blob/5a528b27a2629d779ee502f2620269374247035d/src/main/java/com/cloudbees/plugins/credentials/CredentialsParameterDefinition.java#L72
https://github.com/jenkinsci/credentials-plugin/blob/5a528b27a2629d779ee502f2620269374247035d/src/main/java/com/cloudbees/plugins/credentials/CredentialsParameterValue.java#L35