bts_tests: do not define bs_ag_blks_res in multiple locations

The parameter bs_ag_blks_res is currently defined in ts_SI3_default and
in each PagingTestCfg record. When the parameter is changed in
PagingTestCfg it must be changed in ts_SI3_default as well in order to
have coherent settings in the stestsuit and in the BTS. This can be
quite confusing so lets use the setting from ts_SI3_default when
populating PagingTestCfg to have the value of the constant in one place
only.

Change-Id: I5cbdb31c8398aa241faca34e850388d5e1682167
Related: OS#1575
diff --git a/bts/BTS_Tests.ttcn b/bts/BTS_Tests.ttcn
index 890be91..fd2e50f 100644
--- a/bts/BTS_Tests.ttcn
+++ b/bts/BTS_Tests.ttcn
@@ -1692,9 +1692,10 @@
  *  - that CCCH LOAD IND (PCH) are being generated
  *  - that CCCH LOAD IND (PCH) [no load] is received after paging flood is over */
 testcase TC_paging_imsi_80percent() runs on test_CT {
+	var SystemInformation si3 := valueof(ts_SI3_default);
 	var PagingTestCfg cfg := {
 		combined_ccch := true,
-		bs_ag_blks_res := 1,
+		bs_ag_blks_res := si3.payload.si3.ctrl_chan_desc.bs_ag_blks_res,
 		load_factor := 0.8,
 		exp_load_ind := true,
 		exp_overload := false,
@@ -1715,9 +1716,10 @@
  *  - that CCCH LOAD IND (PCH) are being generated
  *  - that CCCH LOAD IND (PCH) [no load] is received after paging flood is over */
 testcase TC_paging_tmsi_80percent() runs on test_CT {
+	var SystemInformation si3 := valueof(ts_SI3_default);
 	var PagingTestCfg cfg := {
 		combined_ccch := true,
-		bs_ag_blks_res := 1,
+		bs_ag_blks_res := si3.payload.si3.ctrl_chan_desc.bs_ag_blks_res,
 		load_factor := 0.8,
 		exp_load_ind := true,
 		exp_overload := false,
@@ -1738,9 +1740,10 @@
  *  - that CCCH LOAD IND (PCH) are being generated and reach 0 at some point
  *  - that CCCH LOAD IND (PCH) [no load] is received after paging flood is over */
 testcase TC_paging_imsi_200percent() runs on test_CT {
+	var SystemInformation si3 := valueof(ts_SI3_default);
 	var PagingTestCfg cfg := {
 		combined_ccch := true,
-		bs_ag_blks_res := 1,
+		bs_ag_blks_res := si3.payload.si3.ctrl_chan_desc.bs_ag_blks_res,
 		load_factor := 2.0,
 		exp_load_ind := true,
 		exp_overload := true,
@@ -1763,9 +1766,10 @@
  *  - that CCCH LOAD IND (PCH) are being generated and reach 0 at some point
  *  - that CCCH LOAD IND (PCH) [no load] is received after paging flood is over */
 testcase TC_paging_tmsi_200percent() runs on test_CT {
+	var SystemInformation si3 := valueof(ts_SI3_default);
 	var PagingTestCfg cfg := {
 		combined_ccch := true,
-		bs_ag_blks_res := 1,
+		bs_ag_blks_res := si3.payload.si3.ctrl_chan_desc.bs_ag_blks_res,
 		load_factor := 2.0,
 		exp_load_ind := true,
 		exp_overload := true,