SSTableIndexWriter#abort() should log more quietly in cases where an exception is not provided

patch by Caleb Rackliffe; reviewed by Jon Meredith for CASSANDRA-20695

Author: maedhroz

CHANGES.txt

@@ -1,4 +1,5 @@
 5.0.5
+ * SSTableIndexWriter#abort() should log more quietly in cases where an exception is not provided (CASSANDRA-20695)
  * Avoid availability gap between UP and queryability marking for already built SAI indexes on bounce (CASSANDRA-20732)
  * Make Commitlog flush data safely in Direct IO mode (CASSANDRA-20692)
  * Get SAI MemtableIndex refs before SSTableIndex refs at query time (CASSANDRA-20709)

src/java/org/apache/cassandra/index/sai/disk/v1/SSTableIndexWriter.java

@@ -152,7 +152,12 @@ public void abort(Throwable cause)
     {
         aborted = true;
 
-        logger.warn(index.identifier().logMessage("Aborting SSTable index flush for {}..."), indexDescriptor.sstableDescriptor, cause);
+        String message = index.identifier().logMessage("Aborting SSTable index flush for {}...");
+
+        if (cause == null)
+            logger.debug(message, indexDescriptor.sstableDescriptor);
+        else 
+            logger.warn(message, indexDescriptor.sstableDescriptor, cause);
 
         // It's possible for the current builder to be unassigned after we flush a final segment.
         if (currentBuilder != null)