Update the DRN weights webroot url

[alexchernykh]

Hey, the DRN weights in pytorch/models/drn.py for the webroot are not available anymore. According to the issue in the original DRN repo it is now 'http://dl.yf.io/drn/'

[mmv87]

Is it working drn_d_54-0e0534ff.pth now available in 'http://dl.yf.io/drn/' ?

[Debasrita]

http://dl.yf.io/drn/ is down. Can someone provide any alternative link?