Before requesting a scan, check the time threshold
Currently we don't follow the documented way to check requestScan results and if it has succeeded.
This ends up generating, retries and warning such as :
plasma-nm: Wireless scan on "wlp2s0" failed: "Scanning not allowed immediately following previous scan"
This patch checks if the device has not finished a scan within the last 10 seconds and that the last scan finished before allowing more scans to be requested.
RequestScan Doc :
10 seconds request scan threshold in NetworkManager :
Depends on D23576
Reviewers: Plasma, jgrulich
Reviewed By: jgrulich
Differential Revision: https://phabricator.kde.org/D23578