bts: Instruct trxcon for TA=2 at every testcase start

as fake_trx keeps running during the entire test suite run, and
the protocol being UDP based, it doesn't know when BTS_Test will
re-start and hence the old TA/FAKE_TIMING value will remain until
it is set.

Let's explicitly set a FAKE_TIMING of two bits at start-up of each
test case during f_init()

Change-Id: I9f07768346e0d68a4dbe36780e36b799d27a7f06
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 8800139..45fcb06 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -212,6 +212,10 @@
 	/* SI2 + SI4 are required for SI testing as they are mandatory defaults */
 	f_rsl_bcch_fill(RSL_SYSTEM_INFO_2, ts_SI2_default);
 	f_rsl_bcch_fill(RSL_SYSTEM_INFO_4, ts_SI4_default);
+
+	/* start with a default moderate timing offset equalling TA=2 */
+	f_main_trxc_connect();
+	BB_TRXC.send(ts_TRXC_Send(g_bb_trxc_conn_id, ts_TRXC_FAKE_TIMING(2*256)));
 }
 
 /* Attach L1CTL to master test_CT (classic tests, non-handler mode) */
@@ -599,7 +603,6 @@
 	f_init(testcasename());
 	f_init_l1ctl();
 	f_l1_tune(L1CTL);
-	f_main_trxc_connect();
 	f_sleep(1.0);
 
 	/* default max-ta is 63 (full range of GSM timing advance */