kcms/baloo: Fix state checking and button behaviour

Currently currentlyIndexing function always returns true as monitor.IndexerState isn't a thing. This causes the button to always show "Pause Indexer".

This MR fixes the issue of the IndexerState state enum being checked incorrectly in the switch statement, and also the QQC2.Button text being show incorrectly no matter whether the indexing is suspended or not. The reason currentlyIndexing function cannot be used in the button text is because it also has values of Idle, LowPowerIdle, Unavailable, Startup that should show "Pause Indexer" as the indexer is still enabled even if it has nothing to do at the moment.