[BugFix] Fix the problem of label_padding_value not work in warpAffine

[LutaoChu]

solve #2053

test code

from PIL import Image
import cv2
import numpy as np
from paddleseg.transforms import RandomAffine

path = 'data/mini_supervisely/Annotations/ache-adult-depression-expression-41253.png'
label = Image.open(path)
label = np.array(label)
path = 'data/mini_supervisely/Images/ache-adult-depression-expression-41253.jpg'
img = cv2.imread(path)

transform = RandomAffine()
img, label = transform(img, label)
print(img)
print(label)