Site Maintenance status message incomplete

The system message is not clear about site maintenace mode status due to the bug described below. While this is a very minor bug it could be confusing to new drupal admins to think "The checkbox says I am online but the line at the top of the screen says I am offline... which is it?"

When going offline the system.module generates 2 messages at the top of the content area stating:

* The configuration options have been saved.
* Operating in off-line mode.

While in offline mode the latter of these two lines will remain persistent on all screens.

When returning from offline mode the system.module generates only 1 message stating:

* The configuration options have been saved.

The persistent "Operating in off-line mode." is made non-persistent but it is not cleared from the content area and so immediately after returning online the message box reads as follows:

* Operating in off-line mode.
* The configuration options have been saved.

Suggest adding a simple status message so that after returning online the content area says:

* The configuration options have been saved.
* Site Maintenance mode ended. Now operating in on-line mode.

Thank you for your time.