modem: deactive_context: Log when context is successfully deactivated

Change-Id: Ibe40a954aa4548e54b48c444014d7dbd2da9d956
diff --git a/src/osmo_gsm_tester/modem.py b/src/osmo_gsm_tester/modem.py
index 8de3f9f..f0a0b24 100644
--- a/src/osmo_gsm_tester/modem.py
+++ b/src/osmo_gsm_tester/modem.py
@@ -618,6 +618,7 @@
         ctx = systembus_get(ctx_id)
         ctx.SetProperty('Active', Variant('b', False))
         event_loop.wait(self, lambda: ctx.GetProperties()['Active'] == False)
+        self.log('context deactivated', path=ctx_id)
 
     def sms_send(self, to_msisdn_or_modem, *tokens):
         if isinstance(to_msisdn_or_modem, Modem):