[applets/devicenotifier] Don't open popup for already-connected devices
requested to merge ngraham/plasma-workspace:fix-devicenotifier-opening-when-removable-drive-was-already-plugged-in-at-login into master
The old applet only opened the popup when a new device was attached after the applet was loaded, not if there was already a device attached when the applet was loaded. This commit brings back the old behavior by re-using the approach taken in the old applet.
To test, attach a device and restart plasmashell. With the MR, the popup will not open after plasmashell launches. It will still open if you attach a device later.
BUG: 426990 FIXED-IN: 5.20