bug: hold and release

When enable holdAndRelease, the GateController holds the mac module in advance. Specifically, it holds the macModule transfer time of 220 bits early (see the following codes)

int bitsToWait = INTERFRAME_GAP_BITS.get() + kFramePreemptionMinNonFinalPayloadSize.get() + FramePreemptionMinFinalPayloadSize.get() + 4;

However, kFramePreemptionMinNonFinalPayloadSize and FramePreemptionMinFinalPayloadSize is represented in Bytes but not bits, which result in incorrect calculation.

In fact, I'd like to know if we could specify the macModule holding or not with a separate xml file.