private void injectFault() throws IOException {
      if (this.fault.get() && getPos() >= faultPos) {
        throw new IOException("Fault injected");
      }
    }
Faulty file system that will fail if you write past its fault position the FIRST TIME only;
thereafter it will succeed. Used by {@link TestHRegion} too.
hbase-server/src/test/java/org/apache/hadoop/hbase/regionserver/TestHStore.java