timeslot_fsm: Name TS FSM instances on allocation.

Before this patch FSM instances of configured but not connected BTS's
look like this:
FSM Instance Name: 'timeslot[0x612000004a20]', ID: '(null)'
 Log-Level: 'DEBUG', State: 'NOT_INITIALIZED'

Now they look like this:
FSM Instance Name: 'timeslot(0-0-7-NONE)[0x612000004a20]', ID: '0-0-7-NONE'
 Log-Level: 'DEBUG', State: 'NOT_INITIALIZED'

which makes it possible to attribute them to where they belong.
Otherwise, they look like lingering or leaking unattributed FSM
instances.

Change-Id: Idc74ea142b96323b48826f8a52e13e45d535512a

src/osmo-bsc/timeslot_fsm.c

@@ -63,6 +63,7 @@ void ts_fsm_alloc(struct gsm_bts_trx_ts *ts)
 	OSMO_ASSERT(ts->trx);
 	ts->fi = osmo_fsm_inst_alloc(&ts_fsm, ts->trx, ts, LOGL_DEBUG, NULL);
 	OSMO_ASSERT(ts->fi);
+	ts_fsm_update_id(ts);
 }
 
 enum lchan_sanity {