test fix (openfoodfacts#285)

Impacted files:
* `api_addProductImage_test.dart`: renamed tests
* `api_saveProduct_test.dart`: added a specifically larger time out for a slow test
* `corn_da.jpg`: reduced the size from 4000x3000 (2.5Mb) to 1000x750 (200Kb) as it seemed to be problematic, while size was not part of the test

test/api_addProductImage_test.dart

@@ -24,7 +24,7 @@ void main() {
       expect(status.error, 'Dieses Foto wurde schon hochgeladen.');
     });
 
-    test('add ingredients image test', () async {
+    test('add ingredients image test 1', () async {
       SendImage image = SendImage(
         lang: OpenFoodFactsLanguage.ENGLISH,
         barcode: '0048151623426',
@@ -40,7 +40,8 @@ void main() {
       expect(status.error, 'This picture has already been sent.');
     });
 
-    test('add ingredients image test', () async {
+    // TODO(monsieurtanuki): test with a bigger pic used to crash (4000x3000, 2.5Mb)
+    test('add ingredients image test 2', () async {
       SendImage image = SendImage(
         lang: OpenFoodFactsLanguage.DANISH,
         barcode: '5722970900207',

test/api_saveProduct_test.dart

@@ -85,7 +85,11 @@ void main() {
       );
 
       testProductResult1(result2);
-    });
+    },
+        timeout: Timeout(
+          // this guy is rather slow
+          Duration(seconds: 90),
+        ));
 
     test('dont overwrite language', () async {
       String barcode = '4008391212596';