Fix warnings and TestEmptyInput test

This commit fixes various warnings for the windows dashboards and
warnings due to unused variables when compiling in release mode. Further,
TestEmptyInput was failing on vtkPUnstructuredGhostDataGenerator, which,
was not checking for empty input. Fixed that.

Change-Id: I9d7154d0be9af6b42516b136f489619ddd1b3e85
Merge topic 'fix-warning' into master

e9ebae9a Fix warnings and TestEmptyInput test