BSC_Tests: fix a race condition in TC_fh_params_handover_cmd

As can be seen from ttcn3-bsc-test run #1565 on Jenkins [1], it may
happen that the VTY command requesting handover reaches the IUT earlier
than the SCCP 'SACK CC' message.  In this case, the 'SUBSCR_CONN' FSM
remains in state 'WAIT_CC', so we get an error:

  (bts=0,trx=0,ts=0,ss=0) (ARFCN 871) --> BTS 1 Manually triggering Handover from VTY
  SUBSCR_CONN(msc0-conn204)[0x5633b2877af0]{WAIT_CC}: Received Event HANDOVER_START
  SUBSCR_CONN(msc0-conn204)[0x5633b2877af0]{WAIT_CC}: Event HANDOVER_START not permitted

The easiest way to avoid this is to introduce and artificial delay
after the connection establishment and before triggering the handover.

[1] https://jenkins.osmocom.org/jenkins/view/TTCN3/job/ttcn3-bsc-test/1565/

Change-Id: I19f7ca942e22d7930a56d1a525414f137a9ef831
diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index 5f1217b..1f4a615 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -8884,6 +8884,7 @@
 
 	/* Establish a dedicated channel, so we can trigger handover */
 	dt := f_est_dchan(f_rnd_ra_cs(), 23, f_rnd_octstring(16));
+	f_sleep(0.5);
 
 	/* Trigger handover from BTS0 to BTS1 */
 	f_bts_0_cfg(BSCVTY, { "neighbor bts 1" });