DERBY-3838; Convert derbynet/DerbyNetAutoStart to JUnit
  backport of revision 1461415 from trunk. Required addition of getBasePort method 
  into TestConfiguration.


git-svn-id: https://svn.apache.org/repos/asf/db/derby/code/branches/10.9@1462304 13f79535-47bb-0310-9956-ffa450edef68