[AppStream Runner] Reduce verbosity of log output

Authored by bruns on Sep 6 2018, 11:53 PM.

Description

[AppStream Runner] Reduce verbosity of log output

Summary:
Its rather pointless to spew an error message each time a query is done.
Output the warning message just once (on the default logging level), and
output further messages only at debug level.

Reviewers: Plasma, ngraham, davidedmundson

Reviewed By: Plasma, davidedmundson

Subscribers: apol, plasma-devel

Tags: Plasma

Differential Revision: https://phabricator.kde.org/D14806