[FLINK-4259] Added statement in FileCache to close the FSDataOutputStream object

Closes #2299
diff --git a/flink-runtime/src/main/java/org/apache/flink/runtime/filecache/FileCache.java b/flink-runtime/src/main/java/org/apache/flink/runtime/filecache/FileCache.java
index 99ed934..b5bdcaf 100644
--- a/flink-runtime/src/main/java/org/apache/flink/runtime/filecache/FileCache.java
+++ b/flink-runtime/src/main/java/org/apache/flink/runtime/filecache/FileCache.java
@@ -259,6 +259,8 @@
 					IOUtils.copyBytes(fsInput, lfsOutput);
 					//noinspection ResultOfMethodCallIgnored
 					new File(targetPath.toString()).setExecutable(executable);
+					// closing the FSDataOutputStream
+					lfsOutput.close();
 				}
 				catch (IOException ioe) {
 					LOG.error("could not copy file to local file cache.", ioe);