Changes

s1ap_proxy: clarify a logging statement, reduce verbosity

Logging all S1AP PDUs at INFO is way to verbose, use DEBUG.
Clarify that this is the Rx (receive) direction.

Change-Id: I325758c7fb632dc67d0d9cf1f2e58ca337e7a744

s1ap_proxy: add types for S1AP PDU and IE tuples

Change-Id: I39e0a12aade5e31c414cb639dbf333af2a5b7be4

s1ap_proxy: print unique E-RAB ID in error messages

Include the {MME,ENB}-UE-S1AP-ID when printing error messages.
Printing E-RAB-ID may be misleading.

Change-Id: I7327e25ea407b3a21706e8b5e4487135675d91d5

s1ap_proxy_test: re-generate E-RAB RELEASE.{cmd,rsp} PDU blobs

These PDU blobs contained the right E-RAB-ID=6, but different
and unexpected {MME,ENB}-UE-S1AP-ID values.  As a result of this,
the E-RAB {7,9,6} that we establish in test_e_rab_setup/1 is never
released properly, and this is why we're seeing these two errors:

  E-RAB {1,0,6} is not registered (s1ap_proxy:handle_ie/2)
  E-RAB {2,1,6} is not registered (s1ap_proxy:handle_ie/2)

The new S1AP PDU blobs were re-generated using ttcn3-s1gw-test.

Change-Id: I229c47148fd7408e44f1339ae2a2909f570c73ec