- PRACH Configuration Index = 98 is not suSpported by the Amarisoft UE simulator, as a number of PRACH occasions within the PRACH slot is > 1
- for PRACH Configuration Index = 100, number of time-domain PRACH occasions within a PRACH slot is 1

Multiple DUs host cells, whose cell ID cannot match (to identify them
uniquely). Hence, don't check for equality with CU, because otherwise,
we can never connect multiple DUs.

This is a workaround for a problem described in #706. In short, we
cannot reuse the cu_add/remove_f1_ue_data() functions if we are in an
integrated CU-UP/CP ("CU"), but then we can also not reliably use
different UE IDs in CU-UP and CU-CP (except if using even more hacks).

An assoc_id of 0 is used to mark UEs whose DU is "offline" (not
connected). In this patch, if a DU disconnects, we go through all UEs
and set their assoc_id to 0 if they belong to a UE that just went
offline.