Can not enable DMS logging via CDK

[Steve-Pactera]

hashicorp/terraform-provider-aws#1513

The Terraform issue above meets the same problem. It turns out to be the limitation of the AWS API. Thus, when setup task settings of DMS in CDK, if we enable the EnableLogging an error will occur.

In this case, we will not enable the DMS logging in CDK, but barely create a log group and a log stream, which should be manually set up after the stack has been created.