A previous patch added ss7_instance primary_pc validity checks by means of
OSMO_SS7_PC_INVALID. To be consistent, also adjust sccp_user accordingly.
(see I7f0f0c89b7335d9da24161bfac8234be214ca00c)
Remove the osmo_sccp_user's pc_valid field, replaced by pc=OSMO_SS7_PC_INVALID.
Adjust all code paths.
Simplify some log printing, using the fact that osmo_ss7_pointcode_print() now
outputs "(no PC)" for unset point codes.
Change-Id: I8684c9b559712072c772012890bbf7efa7c8eb35
Harald Welte
Neels Hofmeyr