@Override
      public Void answer(InvocationOnMock invocation) throws Throwable {
        throw new IOException("Forced IOException in member acquireBarrier");
      }
Make sure we call cleanup etc, when we have an exception during
{@link Subprocedure#acquireBarrier()}.
hbase-server/src/test/java/org/apache/hadoop/hbase/procedure/TestProcedureMember.java