Changes

stp: Fix brokeness in STP_Tests_M3UA.TC_tmt_loadshare

The test was not even setting the traffic-mode in the IUT.
Furthermore, it was expecting pure round-robin behavior, which was the
older behavior of osmo-stp when loadshare traffic-mode was selected.

Actually split the test into 2, naming them properly (since round robin
is not a AS traffic mode in itself, but a possible implementation of the
loadshare traffic-mode.

The new test validates the usual loadshare traffic-mode based on SLS
distribution.

Related: SYS#7112
Depends: libosmo-sigtran.git Change-Id I61340549c596f1c04bc2269dbc165c327bf72037
Change-Id: I16d81cb2f88bb2927f248182ad4f8f27c8c24859

stp: Fix brokeness in STP_Tests_IPA.TC_tmt_loadshare

Similar to previous commit for M3UA, this time for IPA.
Since in IPA so far the SLS is fixed per ASP, we need to add an extra
sender ASP which will get a new asp_id (and hence SLS) so that we can
also test traffic being sent/distributed to the 2nd receiver.

Change-Id: I61c3efbf8e30533d051e2de506f7c8eaae7e297b

stp: STP_Tests.ttcn: Use M3UA PC and RCTX from config

Change-Id: I81c8402d5ccd6e59f2a6869927c637fff30cb952