Fix empty values for remapUVSetsTo

[dj-mcg]

This fixes this test for environments with remapUVSetsTo defaults configured

[seando-adsk]

@dj-mcg Hi Dan, our devs have some comments/questions about this change.

Doesn't this change hide any problem that could happen with our default values by never letting them be tested?

This change is not problematic for us, but raises the question about accommodating users with custom environments that override default values.

Where is "remapUVSetsTo" default getting modified? Is it a custom plugin you are using internally?

[dj-mcg]

Yes, we're defining studio specific defaults for import and export behavior in a plugin, so this test fails for us unless we explicitly override it with an empty stringPairVector mapping. Simply passing an empty list falls back to whatever default is defined by the runtime environment. If an empty list is intended to override custom defaults, we may have to change how the userArgs are parsed in jobArgs.cpp