transfer: Fix chunked-encoding upload bug

- When uploading via chunked-encoding don't compare file size to bytes
  sent to determine whether the upload has finished.

Chunked-encoding adds its own overhead which why the bytes sent is not
equal to the file size. Prior to this change if a file was uploaded in
chunked-encoding and its size was known it was possible that the upload
could end prematurely without sending the final few chunks. That would
result in a server hang waiting for the remaining data, likely followed
by a disconnect.

The scope of this bug is limited to some arbitrary file sizes which have
not been determined. One size that triggers the bug is 475020.

Bug: https://github.com/curl/curl/issues/2001
Reported-by: moohoorama@users.noreply.github.com

Closes https://github.com/curl/curl/pull/2010

lib/transfer.c

@@ -238,9 +238,11 @@ CURLcode Curl_fillreadbuffer(struct connectdata *conn, int bytes, int *nreadp)
     }
 #endif /* CURL_DOES_CONVERSIONS */
 
-    if((nread - hexlen) == 0)
+    if((nread - hexlen) == 0) {
       /* mark this as done once this chunk is transferred */
       data->req.upload_done = TRUE;
+      infof(data, "Signaling end of chunked upload via terminating chunk.\n");
+    }
 
     nread += (int)strlen(endofline_native); /* for the added end of line */
   }
@@ -1046,7 +1048,8 @@ static CURLcode readwrite_upload(struct Curl_easy *data,
 
     k->writebytecount += bytes_written;
 
-    if(k->writebytecount == data->state.infilesize) {
+    if((!k->upload_chunky || k->forbidchunk) &&
+       (k->writebytecount == data->state.infilesize)) {
       /* we have sent all data we were supposed to */
       k->upload_done = TRUE;
       infof(data, "We are completely uploaded and fine\n");