Change vultr_user.acl to typeset as the ordering is not important and causes extraneous plans

[F21]

Description

This PR changes the acl property in the vultr_user resource from TypeList to TypeSet. The order of the ACLs is not important and due causes a lot of extraneous plans when the order of the ACLs do not match the order returned from the server.

Related Issues

Closes #494

Checklist:

• Have you checked to ensure there aren't other open Pull Requests for the same update/change?
• Have you linted your code locally prior to submission?
• Have you successfully ran tests with your changes locally?

[optik-aper]

Thanks for this! Unfortunately, this won't work without changing how the ACL field is converted to a slice when creating and updating.

panic: interface conversion: interface {} is *schema.Set, not []interface {}

I took a look and this should be added to accommodate the type change.

	acl, aclOK := d.GetOk("acl")
	acls := acl.(*schema.Set).List()

	var aclReq []string
	if aclOK {
		for i := range acls {
			aclReq = append(aclReq, acls[i].(string))
		}

		userReq.ACL = aclReq
	}

You can replace the conversion logic in the create and also replace it in the update

[F21]

Thanks for catching this! I updated the type assertions in the create and update functions.

[optik-aper]

Tested and working. Thanks!