refactor(dms): refactor kafka user

[saf3dfsa]

What this PR does / why we need it:
refactor kafka user
Which issue this PR fixes:
(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)
fixes #xxx

Special notes for your reviewer:

Release note:

refactor kafka user

PR Checklist

• Tests added/passed.

make testacc TEST="./huaweicloud/services/acceptance/dms" TESTARGS="-run TestAccDmsKafkaUser_basic"
==> Checking that code complies with gofmt requirements...
TF_ACC=1 go test ./huaweicloud/services/acceptance/dms -v -run TestAccDmsKafkaUser_basic -timeout 360m -parallel 4
=== RUN   TestAccDmsKafkaUser_basic
=== PAUSE TestAccDmsKafkaUser_basic
=== CONT  TestAccDmsKafkaUser_basic
--- PASS: TestAccDmsKafkaUser_basic (917.24s)
PASS
ok      github.com/huaweicloud/terraform-provider-huaweicloud/huaweicloud/services/acceptance/dms       917.297s

• Documentation updated.

• Schema updated.

• CheckDeleted.

  • a. During query operation (Read Context)
    aa. Resource not found
    >>>>>> Paste the screenshot here <<<<<<

  • b. During delete/disassociate/unbind operation (Delete Context)
    ba. Resource not found
    >>>>>> Paste the screenshot here <<<<<<