Use unique incrementing value for BTS CellId

Change-Id: If4559b945a3e71f3a36fd7ac760cb094278f6b39
diff --git a/src/osmo_gsm_tester/templates/osmo-bsc.cfg.tmpl b/src/osmo_gsm_tester/templates/osmo-bsc.cfg.tmpl
index 14aa62d..d79bb2b 100644
--- a/src/osmo_gsm_tester/templates/osmo-bsc.cfg.tmpl
+++ b/src/osmo_gsm_tester/templates/osmo-bsc.cfg.tmpl
@@ -44,7 +44,7 @@
  bts ${loop.index}
   type ${bts.osmobsc_bts_type}
   band ${bts.band}
-  cell_identity 0
+  cell_identity ${bts.cell_identity}
   location_area_code ${bts.location_area_code}
   training_sequence_code 7
   base_station_id_code ${bts.base_station_id_code}