RRC: ignore random value during RRC Setup Request
This MR is intended to fix the following: When there are consecutive RACH attempts from a particular UE, the CU crashes due to an AssertFatal(false, "not implemented\n"); when the UE is using the same random value but under a different RNTI. This causes the CU to crash very frequently under multi-UE scenarios in our setup.
The current comment in the code, I quote "new UE rnti (coming with random value) is already there, removing UE %x from MAC/PHY", says that there is a need to remove the UE from the MAC/PHY, which I think it is unnecessary. Thus, simply ignore this check.
With this fix, the stability of our network has been significantly improved for multi-UEs (up to 7 in our setup), and no CU crashes were reported after continuous stress-testing for more than half an hour.