BTS_Tests: properly release TCH in f_TC_speech_no_rtp()

Otherwise we're getting a DTE when trying to run this function more
than once in a single testcase (e.g. when testing different channel
modes).  This is already done properly in f_TC_speech_rtp().

Change-Id: I290789153bea4b128af29dcf7c52da16b64c4108
Related: SYS#5919, OS#4823
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 5a34a8c..9482561 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -8278,6 +8278,8 @@
 
 	f_rsl_chan_deact();
 	f_L1CTL_DM_REL_REQ(L1CTL, g_chan_nr);
+	f_rsl_chan_deact();
+	f_rslem_unregister(0, g_chan_nr);
 }
 testcase TC_speech_no_rtp_tchf() runs on test_CT {
 	var ConnHdlr vc_conn;