Move check for previous value of "closed" outside of lambda (#1058)

JAVA-4821

Author: jyemin

driver-sync/src/main/com/mongodb/client/gridfs/GridFSUploadStreamImpl.java

@@ -138,12 +138,14 @@ public void write(final byte[] b, final int off, final int len) {
 
     @Override
     public void close() {
-        withLock(closeLock, () -> {
-            if (closed) {
-                return;
-            }
+        boolean alreadyClosed = withLock(closeLock, () -> {
+            boolean prevClosed = closed;
             closed = true;
+            return prevClosed;
         });
+        if (alreadyClosed) {
+            return;
+        }
         writeChunk();
         GridFSFile gridFSFile = new GridFSFile(fileId, filename, lengthInBytes, chunkSizeBytes, new Date(),
                 metadata);

driver-sync/src/test/functional/com/mongodb/client/gridfs/GridFSBucketSmokeTestSpecification.groovy

@@ -84,6 +84,7 @@ class GridFSBucketSmokeTestSpecification extends FunctionalSpecification {
             def outputStream = gridFSBucket.openUploadStream('myFile')
             outputStream.write(contentBytes)
             outputStream.close()
+            outputStream.close() // check for close idempotency
             fileId = outputStream.getObjectId()
         }