Use unique incrementing value for BTS CellId

Change-Id: If4559b945a3e71f3a36fd7ac760cb094278f6b39
diff --git a/selftest/template_test/osmo-nitb.cfg.tmpl b/selftest/template_test/osmo-nitb.cfg.tmpl
index 2559b14..f1508ec 100644
--- a/selftest/template_test/osmo-nitb.cfg.tmpl
+++ b/selftest/template_test/osmo-nitb.cfg.tmpl
@@ -54,7 +54,7 @@
  bts ${loop.index}
   type ${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}