BTS_Tests: explicitly configure Intave in TC_pcu_interf_ind

Starting from [1] osmo-bts does average the interference levels as
defined by the Intave parameter before reporting over the PCUIF.

In TC_pcu_interf_ind we expect to receive an interference report
every 480ms (one SACCH period), so let's the Intave to 1.

[1] osmo-bts.git I3fbaad5dbc3bbd305b3ad4cb4bfb431a42cfbffc

Change-Id: I070b195af8c62454edd8de961cce6be2c120ae48
Related: SYS#5313
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 55bb0ee..72d011d 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -6108,6 +6108,11 @@
 	var PCUIF_send_data sd;
 	timer T;
 
+	/* Set the averaging/reporting period to 480ms */
+	f_init_vty_bsc();
+	f_vty_cfg_bts(BSCVTY, 0, { "interference-meas avg-period 1" });
+	f_vty_transceive(BSCVTY, "drop bts connection 0 oml");
+
 	f_init_with_pcuif();
 	f_TC_pcu_act_req(0, 0, 7, true);
 
@@ -6152,6 +6157,9 @@
 		}
 	}
 
+	/* Reset the averaging/reporting period back to default */
+	f_vty_cfg_bts(BSCVTY, 0, { "interference-meas avg-period 6" });
+
 	Misc_Helpers.f_shutdown(__BFILE__, __LINE__);
 }