Changes

s1ap_proxy: merge process_pdu_safe() with process_pdu()

We always use the _safe() variant, so it makes no sense to
expose the "unsafe" variant as public API.

Change-Id: I91092625ae577d17a1f96db79804c813b878abfc

s1ap_proxy: do not expose {en,de}code_pdu() API

Change-Id: Ifb9f5c1991c31b5383c46e149286f8eb99a778a5

s1ap_proxy: turn this module into a gen_server

This patch makes the s1ap_proxy module self-contained, so API users
no longer need to initialize, maintain, or deinitialize its internal
state, and also no longer need to trap 'EXIT' signals from the child
erab_fsm processes.  These improvements in maintainability and ease
of use come at the cost of an additional process per SCTP
connection, which is manageable.

Change-Id: Id6e4c7ee29ae31edca658e1293601d38e5f43e63

s1ap_proxy: add E-RAB introspection API

This API will be used by the upcoming interactive VTY interface.
Let's also use it unit tests to check persence/absence of E-RAB FSMs.

Change-Id: I43dcfa613a4ee0de5b2f6619911fd92b1675acd6