Fix OFOut test for end-cap R3/R4/R5

The OFOut test enables and disables the OFOut and checks for resulting voltage differences. The are some particularities for the end-cap however:

• R3 (which has two AMACs): the OFOut of the first AMAC is hardwired to the second AMAC. Therefore the OFOut test does not work. The OFOut of the first AMAC is instead tested with the OFIn test of the second R3 AMAC. For that reason, the test is skipped in case of the first R3 AMAC (even slot, type R3_0)
• R4/R5: R4 and R5 PBs are only placed in even slots on the carrier board. In these cases the AMACOf is not read by the MUX on even slots on the carrier board however, but by the next odd slot, i.e. slot+1.

Both of these particularities are addressed in this MR.

Depends on !157 (merged) and !158 (merged).

Tagging @kkrizka