pcu: TC_t3193: Fix test to properly trigger tx of last DL data block

Since osmo-pcu.git 95ec50c9e4821ed1bdd15e9e30da1278ec1280c1, OsmoPCU
doesn't allow receiving a FINAL_ACK in FLOW state. This test was not
written properly and was taking advantage of that permissive logic in
osmo-pcu to trigger the target use case. Fix it to have the PCU send the
last DL data block (FBI=1) so that it can send a PKT DL ACK/NACK with
FinalAck=1 to terminate the DL TBF.

Change-Id: Ibd445bdd5cc1d1ffd810eea157829403b4b65f1f
1 file changed