Greeter's screensaver is Debian branded

Originally created by @spriver on #12370 (Redmine)

The greeter is showing the Debian branded screensaver that is telling “Debian 9” after some time of inactivity. This may be a bit confusing.

Feature Branch: greeter:bugfix/12370-inhibit-idle

Edited May 15, 2020 by spriver

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