bpslaveLoop uses both parallel & snow for communication

[mtmorgan]

send/recvData() via parallel, but snow::closeNode(). Should only use one package (parallel?)

[DarwinAwardWinner]

To my knowledge, the parallel package is supposed to subsume both snow and multicore packages, so presumably it should just be using that one.

[mtmorgan]

The code was such that closeNode came from snow for SnowParam(), but from parallel for MulticoreParam(). It seems to be ok to use parallel::closeNode, finalized in 2582757.