@Override
        public void beforeUpdate(EntryEvent event) throws CacheWriterException {
          clearOp.start();
        }
Tests the condition when a 'put' is in progress and concurrent 'clear' and 'put'(on the same
key) occur. Thus if after Htree ref was set (in 'put'), the region got cleared (and same key
re-'put'), the entry will get recorded in the new Oplog without a corresponding create (
because the Oplogs containing create have already been deleted due to the clear operation).
This put should not proceed. Also, Region creation after closing should not give an exception.
geode-core/src/integrationTest/java/org/apache/geode/internal/cache/OplogJUnitTest.java