The train/val split in domainnet

[FrankZhangRp]

we find that the train sets are kept the same size on all domains as the 'min_data_len' and we think there is a mistake:

FedBN/singleset/single_domainnet.py

Line 120 in 1caf83c

min_data_len = int(min_data_len * 0.05)

[FrankZhangRp]

if the 'trainset' is only 5% of the total dataset, the training process is too toy and unstable with about 100+ samples per client without pretrained weights. We think the train/val split may be 95% / 5%, but in this code is 5% / 5%.