[Baloo] Fix firstRun and config change logic

Summary:
FirstRun should only be set if baloo was *never ever* run before, and
this case is already handled by baloo internally.

Do no try to do a baloo config refresh if it has just been quit.

Also avoid triggering a config update immediately after starting baloo,
it will do another walk of the directory tree.

Reviewers: #baloo, ngraham, #plasma

Reviewed By: #baloo, ngraham

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D27917