enable optional CACC control mode key in fcd-output

[schwamborn]

Should print control mode ("ACC" or "CACC") for CACC CFModel if key "caccControlMode" is enabled in fcd-output, see #6685.

[schwamborn]

Re-opened due to dubious results reported by CERTH.

[namdre]

@schwamborn: I think it is necessary to consult MSGlobals::gComputeLC (true during lane change compuation) before updating the caccControlMode parameters because the functions freeSpeed and followSpeed can also be called during lane changing.

[namdre]

also, happy easter!

[schwamborn]

@namdre So lane changing does not affect the mode? Shouldn't MSGlobals::gComputeLC then be consulted by other code in MSCFModel_CACC::freeSpeed() and MSCFModel_CACC::followSpeed() as well?

[namdre]

The mode that is used to compute safe gaps (ACC,CACC) should of course also be considered during lane changing. However, the fcd-output should only refer to the mode that was used for car-following, hence we must guard before calling setParameter.