common: reset lchan meas state in gsm_ts_release()
lchan->meas (including interf_meas_num and num_ul_meas) is normally only reset by lchan_meas_reset() called from rsl_tx_chan_act_ack() on RSL CHANNEL ACTIVATION. Idle logical channels are never RSL-activated, so their measurement state is never reset via that path.
On an OML link re-establishment, osmo-bts does not exit: abis.c tears down the signalling links, the bts_shutdown FSM powers down all TRXs, and then waits for reconnect. The gsm_bts/trx/ts/lchan structures remain in memory, so stale interf_meas_num survives the reconnect.
This is why we're seeing these ERRORs while running ttcn3-bts-test:
(bts=0,trx=2,ts=4,ss=6) Not enough room to store interference report (0dBm)
Add a lchan_meas_reset() call to gsm_ts_release(), which is called from nm_channel_fsm's NOTINSTALLED on_enter after the TRX is confirmed closed. This is exactly the right moment: the radio is fully stopped, so no new samples arrive.
