Now that the BTLs are moving down to OPAL and becoming available to ORTE, there no longer is a need/desire to push performance in the OOB/TCP component. So we don't need multiple modules driving NICs in parallel, and can drop all the complicated distribution logic. Fall back to the simplified single module model, but retain the ability to run that module in its own progress thread if so directed.

This should eliminate the connectivity issues that have been reported, and will make maintenance of this component much easier.

cmr=v1.8.2:reviewer=jsquyres:subject=simplify the OOB/TCP component