Don't use generic kwargs in v2 Token Generation

We need to allow for people adding other stuff to the tokens however it
shouldn't be available in the standard case where for example a misspelt
variable would be propagated.

This is in line with how v3 is going to handle this same scenario.

Change-Id: I1aad17893574ebc7c3a6b84f4d6ba1cd27932158
Closes-Bug: #1307278