Also, removed the one from modules/python/src2/cv.py and cleared its
executable bit, since it's not a script.

This allows subclasses of CvBoost to override initial weights that
update_weights uses without duplicating its entire implementation.

Backport from master.

replaced wrong check to correct check

sample code : https://github.com/Itseez/opencv/blob/master/samples/cpp/tutorial_code/features2D/SURF_descriptor.cpp

Bug #2888

http://code.opencv.org/issues/2926