@Override
          public void onCompletion(GetBlobResult result, Exception exception) {
            getBlobInfoCallbackCalled.countDown();
            throw new RuntimeException("Throwing an exception in the user callback");
          }
Test that a bad user defined callback will not crash the router.
@param getBlobCallback User defined callback to be called after getBlob operation.
@param getBlobCallbackCalled This latch should be at 0 after {@code getBlobCallback} has been called.
@param checkBadCallbackBlob {@code true} if the blob contents provided by the getBlob operation with the bad
                            callback should be inspected for correctness.
@throws Exception
ambry-router/src/test/java/com/github/ambry/router/GetManagerTest.java