tbf/test: Do RLC based ack instead of just faking

Currently the assignment is completed by manipulating the state of
the TBF objects directly by setting the state fields to fixed values.
This way, the PCU's code that is responsible to update the state
accordingly is not tested.

This commit changes this to simulate RLC Control Acknowledgement
messages instead.

Sponsored-by: On-Waves ehf
2 files changed