bsc CBSP: f_gen_page(): fix generated payload size range

Fix the length calculation to provide a range of [1..82].

f_rnd_int() generates [0..max[ (i.e., < max), so f_gen_page() so far has a
payload len range of [0..81]. We want no zero payload, and we want a maximum of
82 bytes (page max of 88 minus 6 header bytes).

Change-Id: Id521b6038a23dc8e71ea25475bcdef7bc8917531
diff --git a/bsc/BSC_Tests_CBSP.ttcn b/bsc/BSC_Tests_CBSP.ttcn
index 2399c3a..f54de9b 100644
--- a/bsc/BSC_Tests_CBSP.ttcn
+++ b/bsc/BSC_Tests_CBSP.ttcn
@@ -136,7 +136,10 @@
 }
 
 function f_gen_page() return CBSP_IE {
-	var integer len := f_rnd_int(82);
+	/* The maximum CBSP page payload space is 88, but 6 bytes of payload header are added in the first page: the
+	 * maximum length generated here thus is 82. The minimum generated length is 1 (avoiding zero length).
+	 * note, f_rnd_int(82) returns [0..81], so this results in a len ranging [1..82]: */
+	var integer len := 1 + f_rnd_int(82);
 	var octetstring payload := f_rnd_octstring(len);
 	return valueof(ts_CbspMsgContent(payload, len));
 }