Total is not calculated correctly if user changes the measure unit in Measure Distance

[christinebao]

Reported by Autodesk QA:

steps:

1. in Browser, open a basic web layout
2. view map in 1:100000 scale so that we can verify the calculation easily later
3. click 'Measure' button, so there is a Measure Distance dialog in Task pane
4. select Measure units as Kilometers
5. Draw a 1 cm long line on the map, so in Measure dialog, it displays Segment: 1.00 (Kilometers), Total: 1.00 (Kilometers)
6. select Measure units as Meters
7. you will find : the segment: 1.00(Meters), Total: 1.00 (Meters)
8. continue to draw another 2 cm long line on the map

result: the segment: 2000.00(Meters), Total: 2001.00 (Meters)

expected: the segment: 2000.00(Meters), Total: 3000.00 (Meters)

regression: no, it exists in Knight. but Jedi, it does't have such use case (as user can't change the unit).

[christinebao]

Submit to trunk in r8005, branch 2.6Lightsaber in r8006.