Single GPU card is not available on PC

[Aspirinkb]

The get_idle_gpus.py in utils folder is about to detect how many GPU cards are available on the machine. For many users, there is only one GPU card on their PC for graphical display which leads no GPU available (the only one is busy). So, we should fix the issue by change the way of detecting available GPUs.

[Aspirinkb]

I have a GTX 1080 on my PC for training. So I comment the busy_gpus.append(sub_strs[1]) line and add a pass line to ignore the busy GPU detection.

[jiaxiang-wu]

Enhancement required: change the way of detecting available GPUs.

[jiaxiang-wu]

Resolved in the pull request #75