Update documentation to be able to run OAI gNB with OAI UE and COTS UE with the same configuration file

There is still a leak that needs to be fixed in rrc_UE.c
Should properly free NR_BCCH_BCH_Message_t *bcch_message after asn decoder using ASN_STRUCT_FREE()

When using phy-test mode, the RNTI for PDCP/RLC initialization would be
0, incorrectly initializing these layers, fixed in this commit.

Additionally, in this commit, we only trigger the initialization in
cases where the UE context is initialized (before, the RNTI might be 0
in other cases as well).

integration_2022_wk17

See merge request oai/openairinterface5g!1539

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>