fix(metadata): try to fix MetadataImage refCount (#2089)

Author: lifepuzzlefun

core/src/main/scala/kafka/server/metadata/KRaftMetadataCache.scala

@@ -581,6 +581,12 @@ class KRaftMetadataCache(
     val lock = imageLock
     lock.lock()
     try {
+      newImage.retain()
+
+      if (_currentImage != MetadataImage.EMPTY) {
+        _currentImage.release()
+      }
+
       _currentImage = newImage
     } finally {
       lock.unlock()