implement modem and nitb bits for a real test

Change-Id: I1ca3bd874aed1265d83a46340e9b3e469075c7ee
diff --git a/selftest/real_suite/suites/sms/mo_mt_sms.py b/selftest/real_suite/suites/sms/mo_mt_sms.py
index 05be48c..b97d332 100755
--- a/selftest/real_suite/suites/sms/mo_mt_sms.py
+++ b/selftest/real_suite/suites/sms/mo_mt_sms.py
@@ -8,19 +8,18 @@
 ms_mt = suite.modem()
 
 print('start nitb and bts...')
-nitb.add_bts(bts)
+nitb.bts_add(bts)
 nitb.start()
 sleep(.1)
 assert nitb.running()
 bts.start()
 
-nitb.add_subscriber(ms_mo)
-nitb.add_subscriber(ms_mt)
+nitb.subscriber_add(ms_mo)
+nitb.subscriber_add(ms_mt)
 
 ms_mo.connect(nitb)
 ms_mt.connect(nitb)
 wait(nitb.subscriber_attached, ms_mo, ms_mt)
 
 sms = ms_mo.sms_send(ms_mt.msisdn)
-sleep(3)
-wait(nitb.sms_received, sms)
+wait(ms_mt.sms_received, sms)