harmonize RLC and PDCP configurations in nr_DRB_preconfiguration() and fill_default_secondaryCellGroup()

nr_DRB_preconfiguration() is used in phy-test mode by both, OAI UE and gNB, and in all other modes by OAI UE.
Because of inconsistencies, data transfer with OAI UE was only reliably working in phy-test mode.
Ultimately, OAI UE should use nr_DRB_preconfiguration() only in phy-test mode and do proper DRB configuration instead in all other modes!