Fix a bug in the zmq connection strings, attempt to set zmq options.

Attempts to set zmq rate limiting and multicast packet size from the
environment.

Sets ZMQ_RATE to the value of the environment variable ZMQ_RATE if it
exists.

Sets ZMQ_MULTICAST_MTPDU to the value of the environment variable if it exists.

git-svn-id: https://redoubt.ligo-wa.caltech.edu/svn/advLigoRTS/trunk@4746 6dcd42c9-f523-4c6d-aada-af552506706e