With too many incoming tasks, reset measurements to 1ns instead of 0ns

Resoves #26332 where too many tasks occurred while adjustment was happening, the
measurements were reset to 0, and then an assert failed due to tasks executing
in 0 nanoseconds

Author: dakrone

core/src/main/java/org/elasticsearch/common/util/concurrent/QueueResizingEsThreadPoolExecutor.java

@@ -225,7 +225,7 @@ protected void afterExecute(Runnable r, Throwable t) {
                     // - Since taskCount will now be incremented forever, it will never be 10 again,
                     //   so there will be no further adjustments
                     logger.debug("[{}]: too many incoming tasks while queue size adjustment occurs, resetting measurements to 0", name);
-                    totalTaskNanos.getAndSet(0);
+                    totalTaskNanos.getAndSet(1);
                     taskCount.getAndSet(0);
                     startNs = System.nanoTime();
                 } else {