Remove RWD point if RWD cancel button is clicked
Remove RWD point if RWD cancel button is clicked

Work in https://github.com/WikiWatershed/model-my-watershed/pull/2171
preserved RWD map layers on failure. A side-effect of this work was
that the initial RWD point was also preserved on cancellation.

The point is now explicitly removed when the cancel button is clicked.

Refs #2447

WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed,WikiWatershed/model-my-watershed