move SiteOffListener to own Class.

 refs #1698 This also corrects a non-working admin login when site was closed. Also makes the code a little easier to read in the Listener in order to debug.

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | -
| Refs tickets  | #1698
| License       | MIT
| Doc PR        | -