Fix data race in NR UE MSG3 scheduling
Fixed a data race between DL processing of RAR and UL scheduler, which might
result in dropping MSG3.
It was possible that the UL scheduler for the UL slot which RAR indicates as
MSG3 slot was already run by the time the RAR was decoded.
Therefore when DCI for RAR is decoded, assume worst case and halt UL scheduler
for next slot until RAR is decoded solving the data race. This also in turn
halts all later scheduling due to sequential nature of the UL scheduler calls.
Closes#962
Jaroslava Fiedlerova
3bf3b78cb6