Changes

Use default_layer_manager for all ASPs in SCTP-mode=client & m3ua-mode=ASP

With previous behavior, only first ASP configured as SCTPmode=client and
m3ua-mode=ASP in osmo_sccp_simple_client_on_ss7_id() would be applied
the default_layer_manager.
AS a result, if a client app (eg. osmo-bsc) would manually configure 1 ASP
with 2 ASPs (and leave it to dynamic RKM to setup everything at osmo-stp),
it would fail, since the default LM FSM (in charge of waiting for NTFY and
then sending REQ_REG) would only be
applied to the first ASP.
So one would see 1st ASP doing ASPUP+REG_REQ+ASPAC correctly, but the
second one would do ASPUP+ASPAC directly, which would be refused by
osmo-stp since it had no routing context configured for that ASP/AS.

Change-Id: I50f9a088c55ad103cc23758192773fc855747e12