ms_android: set num_carriers to 1 by default

throughput tests require the UE object to have the num_carriers
member. For Android UEs, set it to 1 by default.

Change-Id: I297d24bb578a7db0eb7629be4f2cc0d54624467d

src/osmo_gsm_tester/obj/ms_android.py

@@ -79,6 +79,7 @@ class AndroidUE(MS, AndroidHost, srslte_common):
         self.remote_metrics_file = None
         self.metrics_file = None
         self.brate_mon = None
+        self.num_carriers = 1
 
     def configure(self):
         values = dict(ue=config.get_defaults('androidue'))