meas_vis: use the lchan identity as primary key, not the IMSI
While re-adding meas_feed to osmo-bsc.git, I noticed that the meas_vis and meas_web tools appear to use the lchan's IMSI as primary key to visualizing active lchans. They should use the bts,trx,ts,ss number instead.
meas_vis is currently still in openbsc.git, it should probably move over to osmo-bsc #3191.
meas_web is external, but it could make sense to send a pull request.