text: Title: face_recognition.face_encodings(...) doesn't work on multiprocessing
  Body: * face_recognition version:lastest
  * Python version:3.6
  * Operating System:Ubuntu16.04
  
  ### Description
  
  I was trying to put face_recognition.face_encodings on multiprocessing cause it's time consuming.
  But it seems like face_recognition didn't do anything on sub process.
  
  ### What I Did
      import cv2
      import face_recognition as fr
      import os
      import numpy as np
      from multiprocessing import Process,Pool
      img_list = []
      def multi_process(img):
          cnt=img_list.index( img)+1
          print(cnt)
          locations=fr.face_locations(img,number_of_times_to_upsample=2,model="cnn")
          print(cnt,locations)
          out_path = "./test/faces"
      
          encs = fr.face_encodings(img, locations, 500)
      
          for index, location in enumerate(locations):
              print(out_path + "/%d_%d_%d_%d_%d_%d.jpg" % (cnt, index, location[1], location[0]
                                                           , location[3], location[2]))
              img = cv2.rectangle(img, (location[1], location[0]), (location[3], location[2]), (0, 255, 0), 1)
      
              if not os.path.exists(out_path):
                  os.makedirs(out_path)
              cv2.imwrite(out_path + "/%d_%d_%d_%d_%d_%d.jpg" % (cnt, index, location[1], location[0]
                                                                 , location[3], location[2]), img)
              np.save(out_path + "/%d_%d" % (cnt, index), encs[index])
      def preprocess(video_path):
          cap=cv2.VideoCapture(video_path)
          cnt=0
          out_path="./test/faces"
          while True:
              _,img=cap.read()
              cnt+=1
              if img is None:
                  break
              img_list.append(img)
          pro_cnt=32
          print(len(img_list))
          locations = fr.face_locations(img_list[0], number_of_times_to_upsample=2, model="cnn")
          print(locations)
          for i in range(len(img_list)//pro_cnt):
              p = Pool(pro_cnt)
              for img_i in img_list[i*pro_cnt:i*pro_cnt+pro_cnt]:
                  p.apply_async(multi_process,(img_i,))
              p.close()
              p.join()
      if __name__=="__main__":
          video_path ="/path/to/test.avi" 
          data_base = "./test"
          start=time.time()
          preprocess(video_path)
          end=time.time()
          print(end-start)
  
  ###Thanks
  Pretty thank you all for watching my stupid issue.