viewer#3055 Fix texture fetch being stuck

destroyRawImage is the only function that calls saveRawImage(), not
calling it results in fetcher thinking that it still needs data to do
the saving and looping back to trying to fetch.

indra/newview/llviewertexture.cpp

@@ -1557,8 +1557,8 @@ void LLViewerFetchedTexture::postCreateTexture()
     if (!needsToSaveRawImage())
     {
         mNeedsAux = false;
-        destroyRawImage();
     }
+    destroyRawImage(); // will save raw image if needed
 
     mNeedsCreateTexture = false;
 }