make PCU tests send PS paging requests on BVCI zero

osmo-pcu discards PAGING-PS messages unless received on the
signalling BVCI 0. The BVCI value must be set to zero both
in the NS header and the BSSGP header. Create new ports between
the PCU_Test components which the TC_paging test case can use
to ensure that both layers send frames with BVCI value of zero.

This does not make PCU_Tests.tc_paging work yet, however the PS
paging request is now processed by osmo-pcu rather than discarded.

Change-Id: I0437123b04b7320a4f690f0646578c57abf6bc87
Related: OS#2404
2 files changed