Fixed infinite loop of MultipartBodyTest for master branch.

Author: carryel

api/src/test/java/org/asynchttpclient/multipart/MultipartBodyTest.java

@@ -91,7 +91,7 @@ private static void compareContentLength(final List<Part> parts) {
                 } catch (IOException ie) {
                     Assert.fail("read failure");
                 }
-                if (readBytes >= 0) {
+                if (readBytes > 0) {
                     totalBytes += readBytes;
                 } else {
                     last = true;