Add an addtional SOL block to enforce request channel bandwidth

To solve the issue #374 for the first deployment, pull request #390 tries to have multiple SOL blocks to spread the load from GK blocks. Currently, each SOL block enforces ``5%/#SOL`` of the total link bandwidth on the request channel. This is not ideal because some SOL blocks may receive more requests than the other SOL blocks due to the load imbalance, and some requests will be dropped even the aggregated bandwidth of the request traffic doesn't exceed the ``5%`` threshold.

One solution is to let each SOL block enforce ``5%`` of the total link bandwidth on the request channel, and finally add one additional SOL block to enforce the bandwidth limit on the aggregated requests from all SOL blocks.