provider/aws: Support run_command_parameters in aws_cloudwatch_event_target (#14067)
provider/aws: Support run_command_parameters in aws_cloudwatch_event_target (#14067)

```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSCloudWatchEventTarget_'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
2017/04/29 11:00:09 Generated command/internal_plugin_list.go
TF_ACC=1 go test ./builtin/providers/aws -v -run=TestAccAWSCloudWatchEventTarget_ -timeout 120m
=== RUN   TestAccAWSCloudWatchEventTarget_basic
--- PASS: TestAccAWSCloudWatchEventTarget_basic (58.75s)
=== RUN   TestAccAWSCloudWatchEventTarget_missingTargetId
--- PASS: TestAccAWSCloudWatchEventTarget_missingTargetId (36.11s)
=== RUN   TestAccAWSCloudWatchEventTarget_full
--- PASS: TestAccAWSCloudWatchEventTarget_full (90.30s)
=== RUN   TestAccAWSCloudWatchEventTarget_ssmDocument
--- PASS: TestAccAWSCloudWatchEventTarget_ssmDocument (38.64s)
PASS
ok  	github.com/hashicorp/terraform/builtin/providers/aws	223.833s
```
terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,kjmkznr/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,ashinohara/terraform-provider-aws,ashinohara/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,kjmkznr/terraform-provider-aws,ashinohara/terraform-provider-aws,terraform-providers/terraform-provider-aws,charles-at-geospock/terraform-provider-aws,terraform-providers/terraform-provider-aws,ClementCunin/terraform-provider-aws,nbaztec/terraform-provider-aws,terraform-providers/terraform-provider-aws,kjmkznr/terraform-provider-aws,nbaztec/terraform-provider-aws,ClementCunin/terraform-provider-aws,ClementCunin/terraform-provider-aws,ClementCunin/terraform-provider-aws,nbaztec/terraform-provider-aws,nbaztec/terraform-provider-aws,Ninir/terraform-provider-aws,Ninir/terraform-provider-aws,Ninir/terraform-provider-aws,ashinohara/terraform-provider-aws,Ninir/terraform-provider-aws