Delete all the specified ACL users and terminate all the connections that are
authenticated with such users. Note: the special `default` user cannot be
removed from the system, this is the default user that every new connection is
authenticated with. The list of users may include usernames that do not exist,
in such case no operation is performed for the non existing users.

@return

@integer-reply: The number of users that were deleted. This number will not
always match the number of arguments since certain users may not exist.

@examples

```
> ACL DELUSER antirez
1
```