bugfix: set correct default values to 3d pooling padding and stride (#5096)
bugfix: set correct default values to 3d pooling padding and stride (#5096)

* Fix default values of 3d pooling padding and strides

* Set pooling default padding and stride in Init func

* Add pad and kernel length checks

* Fix lint error

Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet,Guneet-Dhillon/mxnet