Fixed media provider performance.

ElementX/Sources/Services/Media/MediaProvider.swift

@@ -30,11 +30,16 @@ struct MediaProvider: MediaProviderProtocol {
     }
     
     func loadImageFromURL(_ url: String, _ completion: @escaping (Result<UIImage, MediaProviderError>) -> Void) {
+        if let image = imageForURL(url) {
+            completion(.success(image))
+            return
+        }
+        
         imageCache.retrieveImage(forKey: url) { result in
             if case let .success(cacheResult) = result,
                let image = cacheResult.image {
                 completion(.success(image))
-            }
+                return
             }
             
             processingQueue.async {
@@ -63,3 +68,4 @@ struct MediaProvider: MediaProviderProtocol {
             }
         }
     }
+}