enb: add abstract method stop()

implement as noop for Amarisoft eNB, srsENB will send q+Enter to stdin,
which is implemented in class srslte_common()

Change-Id: Ide606e1a6b523997215aa2fa39d4d56ae1f49181
diff --git a/src/osmo_gsm_tester/obj/enb_srs.py b/src/osmo_gsm_tester/obj/enb_srs.py
index bf988eb..aee3f61 100644
--- a/src/osmo_gsm_tester/obj/enb_srs.py
+++ b/src/osmo_gsm_tester/obj/enb_srs.py
@@ -119,6 +119,10 @@
         self.dbg('Enabling console trace')
         self.process.stdin_write('t\n')
 
+    def stop(self):
+        # Implemented in srslte_common.py
+        srslte_common.stop(self)
+
     def start_remotely(self):
         remote_env = { 'LD_LIBRARY_PATH': self.remote_inst.child('lib') }
         remote_binary = self.remote_inst.child('bin', srsENB.BINFILE)