Merge and Multiplexer have a race issue

After introduction of a new MergeTest the following race condition has been observed.

Say we have A and B nodes each having one service S. They split and then heal again. Recall that we first install view down the stack and then up the stack. When MergeView travels up the stack to multiplexer we do service view merge consolidation in Multiplexer#handleMergeView.

However, MergeView might arrive at node A at time T and at node B at time T+N msec. What happens is that one node installs view sooner than the other one and then this leads to discarding of service ack messages (in NAKACK layer) during service view merge consolidation.