[Platform] Remove incorrect isProxy check

Errant isProxy check caused node views to fail
to report their parent views in certain situations,
resulting in nasa/mct#261, wherein the Move
option is incorrectly suppressed by dragging
and dropping.

Also included is unit test to exercise method
and detect regression.

```
 Wrote or re-wrote unit tests (Y/N): Y
 Ran entire suite of unit tests successfully (Y/N): Y
 Verified bug fix with the described replication steps or verified the implementation meets the requirement cited (Y/N): Y
 Code coverage requirements satisfied (new code=80%, changed code=at least as high as existing) (Y/N): Y
 Code review date and attendees: Self-review by pull request
 Describe potential impact on other areas of the code: Drag-drop
 Describe any test prerequisites for this fix (e.g., restart the database): N/A
 For bugs marked "Regression - Yes", describe the cause of the regression: N/A
 Did you modify any pom.xml file? If yes, did you thoroughly document your changes and reasons? N
```