bsc: Fix dangling subscriber talloc ctx in f_TC_paging_Nreq

First, page only on BTS0, not all the BTS. This simplifies the test and
also makes the subscriber be refcounted only on BTS0.
Then, drop the OML connection after receiving all the expected paging
requests; it will make the BSC flush the paging queue and hence avoid
TTCN3 checks erroring due to dangling subscriber talloc contexts.

Change-Id: Ibbd9168f3ac2c1cd4f4577644d75499d49c2823f
diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index f514c43..b35d316 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -3607,8 +3607,10 @@
 	}
 
 	for (i := 0; i < num_subscribers; i := i + 1) {
+		/* Page on LAC-CI of BTS0: */
 		BSSAP.send(ts_BSSAP_UNITDATA_req(g_bssap[0].sccp_addr_peer, g_bssap[0].sccp_addr_own,
-			   ts_BSSMAP_Paging(imsis[i], valueof(ts_BSSMAP_CIL_noCell), omit, omit)));
+			   ts_BSSMAP_Paging(imsis[i], valueof(ts_BSSMAP_CIL_LAC_CI({ts_BSSMAP_CI_LAC_CI(1, 0)})),
+			   omit, omit)));
 	}
 
 	T_rx.start;
@@ -3645,6 +3647,9 @@
 		}
 	}
 
+	/* Drop OML connection to have all paging requests flushed: */
+	f_vty_transceive(BSCVTY, "drop bts connection 0 oml");
+
 	f_shutdown_helper();
 }
 /* Verify BSC can schedule 500 paging requests under one minute if BTS buffer is good enough */