Handle GTP receiver errors, fix memory leaks, add CU-UP test - Fix use-after-free bugs in GTP by properly stopping the receive thread(s) - Fix a bug from !3519 (merged): QFI 0 is a valid QFI - Fix multiple memory leaks in CU-UP, E1, CU-UP load tester, SCTP - Add a (conservative) functional CU-UP test that verifies that the load tester and CU-UP work. Test only a low throughput, as it will run in parallel with other tests.