Handle exceptions when deleting networks and ports with NVP

- if network/port doesn't exist in NVP anymore, delete from quark db
- if network/port does exist in NVP, delete from quark db and then add
  info about it to new orphaned db tables for clean-up by sysadmins later

RM6485
Good 'ol Liskov substitution principle.  Agreed.  WIll go back to lswitch_uuid or rename.  Looking at it now.