Remove some variables from the RCRMQ class

The previous design was base on these assumptions:
  RCRMQ instance only need to do either publish or consume
  RCRMQ instance only need to interact with one single queue

However, in order to perform RPC-like call, an instance will need to do both
publish and consume. In addition, publish and consume are not necessary
to the same queue. So, save queue name as single variable inside the
instance is not viable anymore.