instr_keys as parameter for consistency
remove all replacements of previous assertions

(the new code was using inappropriate exception, but anyway the checks are unnecessary)
capture port-instrument associations in simulated network to enable turning on/off port with given instrument ID.  New tests:  test_turn_on_and_off_port and test_turn_on_and_off_port_given_instrument. All of this is part of a more general revision )still ongoing) to capture and handle such associations.
Merge pull request #2113 from carueda/pa_port-intr-assocs

port-instrument associations