MFC: 260791
MFC: 260791

Add a command line argument to turn off blocking waiting for the user
to press Ctrl-C (-b).  This allows tests with tight loops of mcgrabs
that can stress the multicast tables.

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase