Reclaim native memory quicker when using ZlibCompressor (mongodb#1285)

Reclaim native memory quicker by overriding close() on DeflaterOutputStream to invoke end() on the Deflater, since by supplying a deflater to the constructor of DeflaterOutputStream usesDefaultDeflater is set to false and therefore end() is not invoked in DeflaterOutputStream#close.

JAVA-5280

Author: raelg

driver-core/src/main/com/mongodb/internal/connection/ZlibCompressor.java

@@ -18,6 +18,7 @@
 
 import com.mongodb.MongoCompressor;
 
+import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
 import java.util.zip.Deflater;
@@ -48,6 +49,15 @@ InputStream getInputStream(final InputStream source) {
 
     @Override
     OutputStream getOutputStream(final OutputStream source) {
-        return new DeflaterOutputStream(source, new Deflater(level));
+        return new DeflaterOutputStream(source, new Deflater(level)) {
+            @Override
+            public void close() throws IOException {
+                try {
+                    super.close();
+                } finally {
+                    def.end();
+                }
+            }
+        };
     }
 }