yet another vet fix round

Fixes the following vet reports:

```
builtin/providers/atlas/resource_artifact.go:139: arg user for printf verb %d of wrong type: string

builtin/providers/aws/resource_aws_network_acl.go:191: wrong number of args for format in Errorf call: 2 needed but 3 args
builtin/providers/aws/resource_aws_network_acl.go:264: wrong number of args for format in Errorf call: 1 needed but 2 args
builtin/providers/aws/resource_aws_network_acl.go:268: wrong number of args for format in Errorf call: 1 needed but 2 args
builtin/providers/aws/resource_aws_network_acl.go:286: arg m["to_port"].(int) for printf verb %s of wrong type: int
builtin/providers/aws/resource_aws_network_acl_test.go:277: arg r.NetworkAcls for printf verb %s of wrong type: []github.com/mitchellh/goamz/ec2.NetworkAcl
builtin/providers/aws/resource_aws_subnet_test.go:21: arg v.MapPublicIpOnLaunch for printf verb %s of wrong type: bool

builtin/providers/heroku/resource_heroku_app.go:192: arg vs for printf verb %s of wrong type: bool
builtin/providers/heroku/resource_heroku_app.go:198: arg vs for printf verb %s of wrong type: bool

builtin/providers/mailgun/resource_mailgun_domain_test.go:73: arg DomainResp.Domain.Wildcard for printf verb %s of wrong type: bool

command/remote.go:165: wrong number of args for format in Sprintf call: 1 needed but 2 args
```