Update base PyTorch docker 21.12

[Nic-Ma]

Is your feature request related to a problem? Please describe.
@yiheng-wang-nv and I are testing a performance drop issue in the spleen segmentation task when comparing MONAI 0.5 and 0.8. And I found that NVIDIA just released 21.12 PyTorch docker:
https://catalog.ngc.nvidia.com/orgs/nvidia/containers/pytorch
Will update it in MONAI docker and test.