Use unique incrementing value for BTS LAC

Change-Id: I9f864bac05e39ec2fc305f774194799c3d8fe1b0
diff --git a/src/osmo_gsm_tester/bts_sysmo.py b/src/osmo_gsm_tester/bts_sysmo.py
index e8ac7c2..03dc97e 100644
--- a/src/osmo_gsm_tester/bts_sysmo.py
+++ b/src/osmo_gsm_tester/bts_sysmo.py
@@ -29,6 +29,7 @@
     remote_inst = None
     remote_env = None
     remote_dir = None
+    lac = None
 
     REMOTE_DIR = '/osmo-gsm-tester'
     BTS_SYSMO_BIN = 'osmo-bts-sysmo'
@@ -143,6 +144,8 @@
     def conf_for_bsc(self):
         values = config.get_defaults('bsc_bts')
         config.overlay(values, config.get_defaults('osmo_bts_sysmo'))
+        if self.lac is not None:
+            config.overlay(values, { 'location_area_code': self.lac })
         config.overlay(values, self.conf)
         self.dbg(conf=values)
         return values
@@ -150,4 +153,7 @@
     def set_bsc(self, bsc):
         self.bsc = bsc
 
+    def set_lac(self, lac):
+        self.lac = lac
+
 # vim: expandtab tabstop=4 shiftwidth=4