update bake-bulk tests mercury addr usage to match margo tests
Currently, the bake-bulk tests rely on dictating the listening port using BMI so that clients know exactly which address to connect to apriori.
Margo is a little smarter in that the server address to connect to is written to a file in /tmp that the client can read the address from. This gives us more flexibility in using other transports where we may not know the Mercury addr apriori.