remove specific verification regarding platform ports as this aspect is being reviewed and cleanup performed
RSNPlatformDriver: get ports with request to RSN OMS
remove platform port state from network definition (state is more of a runtime aspect while the network definition is mainly intended for static configuration)
capture instrument_ids associated with ports
remove unused code
remove unneeded verification in config validation
PlatformAgent now gets attribute info from PlatformDriver to (instead of directly inspecting the config)
make platform exception extend IonException (per MM email)
raise appropriate exception in PlatformAgent.{on_init,on_start} if bad configuration is provided. This aligns with expected behavior of agents when problems are detected in this calls (in particular, configuration related problems).
move _validate_configuration to on_init (from on_start) in platform agent
use get_agent_process_id method in ResourceAgentClient (previously ResourceAgentClient._get_agent_process_id as that instance method was not originally available)
use _pnode.subplatforms for launching sub-platforms; then, use _pa_clients for subsequent operations against the launched sub-platforms
use _pnode.instruments for launching instruments; then, use _ia_clients for subsequent operations against the launched instruments
update some comments related with OOIION-1495 (no changes in code)
Merge pull request #2171 from carueda/pa_agent_driver_oms_adjustments

platform agent/driver/ci-oms adjustments and more clean-up