[FileIndexScheduler] Force evaluation of indexerState after suspend/resume

Summary:
When the scheduler is idle when suspending scheduleIndexing() has to be
triggered, otherwise indexerState is only evaluated on the first external
trigger (e.g. a changed file).

On resume, scheduleIndexing() never updated the state, as Suspended did
not qualify as an Idle state. This had the effect of the scheduler being
stuck in the Suspended state.

Test Plan:
balooctl suspend && balooctl status
balooctl resume && balooctl status

Reviewers: Baloo, ngraham

Reviewed By: Baloo, ngraham

Subscribers: kde-frameworks-devel

Tags: Frameworks, Baloo

Differential Revision: https://phabricator.kde.org/D27326