The 5G-RFsim F1 test tested multiple DUs at one CU. This
functionality is retained in the new F1+E1 test.

The 5G-RFsim E1 test tested a single CU-UP at a single CU-CP.  Here, we
extend to use multiple CU-UPs, one for each DU. The associated is
ensured by using three different F1-U transport networks, one for each
DU/CU-UP pair.