Property name changes in DefaultCompositionGraph profile on adding new property in DefaultCompositionGraph.

Steps to repro:
1. Create a new HDRP template project
2. Windows > Render Pipeline > HD Render Pipeline Compositor.
3. Enable Compositor > Project Window > Assets/Compositor.
4. Open DefaultCompositionGraph > Blackboard > Add Vector1 > Save Asset.
5. Select DefaultCompositionGraph profile > Property name > Test1.
6.Open DefaultCompositionGraph > Blackboard > Add Vector2 > Save Asset.

Actual Result:
Property name changes in DefaultCompositionGraph profile.

Expected Result:
Property name should not change in DefaultCompositionGraph profile.

Reproducible in:
2020.2.0a19, 2020.1.0f1, 2020.1.0b13 with Package version 9.0.0 preview.33.

Note: HDRP Compositor window introduced in 9.0.0 preview.33.

Environment:
Occurring on Windows 10 & Mac 10.15.