ACCUMULO-2455 Remove JVM reuse, causing some test failures

  Forked JVMs are reused, but a JVM can be left in a bad state, causing
  a cascade of other test failures. This reuse can speed up the tests,
  but I'm disabling it, until we can figure out which tests leave the
  JVM in a bad (non-reusable) state and whether we can actually avoid
  that or not, such that it'd be safe to turn JVM reuse back on.