Fix DyDCNv2 RuntimeError

[BubblyYi]

the parameter of offset is not set as continuous will trigger the runtime error: offset must be continuous

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Modification

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[jbwang1997]

Hello @BubblyYi, thanks for your contributions. Could you provide the error report before this modification?

[BubblyYi]

Hello @BubblyYi, thanks for your contributions. Could you provide the error report before this modification? As you can see, this bug can be reproduced in torch==1.3.0, mmcv==1.3.9,

[BIGWangYuDong]

This PR is to fix errors in lower version PyTorch, which will not affect high version PyTorch