bsc: Fix encoding of 2-digit MNC (paging tests)

The TTCN-3 data types are abstract data types,  Encoding artefacts
like 'F' for padding shouldn't be seen by the user.  Hence, let's
pass a 2-digit-long or 3-digit-long hexstring into the encoder
functions and let them determine if they should introduce any 'F'
for padding or not.

Change-Id: If4d3dfc16381493d7e710be746ed963975051fc1
diff --git a/bsc/BSC_Tests.ttcn b/bsc/BSC_Tests.ttcn
index 355f3e2..a0e0559 100644
--- a/bsc/BSC_Tests.ttcn
+++ b/bsc/BSC_Tests.ttcn
@@ -949,7 +949,7 @@
 	GsmLac		lac,
 	GsmCellId	ci
 };
-private const Cell_Identity cid := { '001'H, 'f01'H, 1, 0 };
+private const Cell_Identity cid := { '001'H, '01'H, 1, 0 };
 
 type set of integer BtsIdList;