minor fix on join

Author: arturobernalg

httpcore5/src/main/java/org/apache/hc/core5/reactor/MultiCoreIOReactor.java

@@ -102,7 +102,9 @@ public final void awaitShutdown(final TimeValue waitTime) throws InterruptedExce
         }
         for (int i = 0; i < this.threads.length; i++) {
             final Thread thread = this.threads[i];
-            thread.join(TimeUnit.NANOSECONDS.toMillis(remainingNanos));
+            final long millis = TimeUnit.NANOSECONDS.toMillis(remainingNanos);
+            final int nanos = (int) (remainingNanos - TimeUnit.MILLISECONDS.toNanos(millis));
+            thread.join(millis, nanos);
             remainingNanos = deadlineNanos - System.nanoTime();
             if (remainingNanos <= 0) {
                 return;