Spotlight: only destroy queries that have beed marked

Signed-off-by: Ralph Boehme <rb@sernet.de>
Spotlight: move init to the right place

Signed-off-by: Ralph Boehme <rb@sernet.de>
Spotlight: fix async query close

* use state flags for marking closed queries
* don't use GCancellables

Additionally add lots of debugging.

Signed-off-by: Ralph Boehme <rb@sernet.de>