Changes

pcu_sock: do not receive a TXT ind. with PCU_VERSION for a specific BTS

We receive a TXT indication that contains the PCU_VERSION from the PCU when the
connection to the PCU is established. This message contains a BTS number, which
is always 0. This is a hard coded value that does not refer to a specific BTS
object. Also it is not logical to inform a specific BTS object about the PCU
version. This information should be directed to the connecting process as a
whole. However, we use this TXT indication to trigger certain initialization
processes on the BTS object we manage inside the BTS process (currently this
is only 1 bts, but this may change in the future). So instead of using the
BTS in the TXT indication, we should iterate of over all BTS objects and
trigger the initializations for each of the BTS objects.

This change does not have any dependencies, nor does it change the current
behavior of osmo-bts. It just cleans up the logic, so that it works by
intension and not just by chance.

Related: OS#6507
Change-Id: I1bb8d0ec5e8d4b9f822f94249a75d8dc477144a3