gprs_ns2: implement a simple load sharing for UDP

Implement the load sharing based on modulo of the LSP. As long the gprs_ns2 doesn't
support the resource distribution function (48.016 ยง 4.4a) this simple
approach is good enought.

Fixes: OS#4836
Change-Id: I8c2fe5d647694886ac600470fca6ea5d5d210a85
diff --git a/tests/gb/gprs_ns2_test.ok b/tests/gb/gprs_ns2_test.ok
index f40579f..40a1528 100644
--- a/tests/gb/gprs_ns2_test.ok
+++ b/tests/gb/gprs_ns2_test.ok
@@ -20,6 +20,14 @@
 ---- Try to receive over blocked NSVC[0]
 ---- Receive over NSVC[1]
 --- Finish unitdata test
+--- Testing unitdata weight test
+---- Create NSE + Binds
+---- Create NSVC[0]
+---- Create NSVC[1]
+---- Create NSVC[2]
+---- Send UNITDATA to all NSVCs
+---- Send BSSGP data to the NSE to test unitdata over NSVC[1]
+--- Finish unitdata weight test
 --- Testing mtu test
 ---- Create NSE + Binds
 ---- Create NSVC[0]