Fixed double-callback for cached images

Summary: public

A missing return statement in RCTImageLoader meant that cached images would be loaded twice - once from cache and again from the source.

This was mostly innocuous, causing only a slight perf regression due to the image cache being effectively disabled, however in some cases (such as RCTImageEditingManager.cropImage) it caused the success callback to fire twice, resulting in a crash.

Reviewed By: fkgozali

Differential Revision: D2684956

fb-gh-sync-id: 7580a6fbfe00a30807951803e04bfcdbee3bb80a

Libraries/Image/RCTImageLoader.m

@@ -290,6 +290,7 @@ - (RCTImageLoaderCancellationBlock)loadImageWithTag:(NSString *)imageTag
     NSCachedURLResponse *cachedResponse = [_URLCache cachedResponseForRequest:request];
     if (cachedResponse) {
       processResponse(cachedResponse.response, cachedResponse.data, nil);
+      return;
     }
 
     // Download image