vrouter: Removing compilation warnings.

Compilation warnings have been fixed.
This test does nothing, because any value provided as index via function call will be automatically converted to unsigned int which means that any index that is provided is >= 0, so this test fails always (this is actually what compiler message says.) To leave that, we would have to change function definition/declaration to accept signed integers (not really a problem.) I have walked through the code and found out that all of invocations (~3 are there) provide variable defined as unsigned  as an actual argument. If someone fails to provide properly cast value we are going to fail inevitably and there is nothing we can do. (we can cast unsigned to signed but are we sure then that the value is actually supposed to be signed?)