Move RELEASING tbf_state transition to tbf_fsm

PdchUlcTest output changes because the original state NULL is not
expected when transactioning to RELEASING upon MAX N310* being hit. In
any case, none of those events should happen in NULL state, but we
don't really care about TBF states there so we are fine with whatever
the state is.

Related: OS#2709
Change-Id: I516b8d989a0d705e5664f8aeaf7d108e0105aa16
diff --git a/tests/tbf/TbfTest.err b/tests/tbf/TbfTest.err
index c6cea78..62a3a51 100644
--- a/tests/tbf/TbfTest.err
+++ b/tests/tbf/TbfTest.err
@@ -3083,6 +3083,7 @@
 PDCH(bts=0,trx=0,ts=7) Expiring FN=2654379 but previous FN=2654318 is still reserved!
 PDCH(bts=0,trx=0,ts=7) Timeout for registered USF (FN=2654318): TBF(TFI=0 TLLI=0xf1223344 DIR=UL STATE=FLOW)
 TBF(TFI=0 TLLI=0xf1223344 DIR=UL STATE=FLOW) N3101 exceeded MAX (10)
+TBF(UL-TFI_0){FLOW}: Received Event MAX_N3101
 TBF(UL-TFI_0){FLOW}: state_chg to RELEASING
 TBF(TFI=0 TLLI=0xf1223344 DIR=UL STATE=RELEASING) starting timer T3169 [MAX N3101 reached] with 5 sec. 0 microsec, cur_fn=2654379
 PDCH(bts=0,trx=0,ts=7) Expiring FN=2654379 but previous FN=2654322 is still reserved!