Avoid port conflict for localDAQ FM

[kakwok]

If we manage to get local run event building xdaqs (TA, eventBuilder, FU) into one executive under a separate FM (localDAQ FM), we will need a mechanism in the FM code to edit the port to communicate with the localDAQ executives.
This is particular essential to support parallel running of two configurations, both taking runs at the same time. If localDAQ executives have a same, static port in both configurations, this will result in port conflicts.
FM should be able to assign a port to the localDAQ executives(and those they talk to) on-the-fly before initializing the executives.