Schedule queries to run later when Hawk is busy
Moved from Bugzilla:
https://bugs.eclipse.org/bugs/show_bug.cgi?id=560859
Hawk becomes unavailable for querying when it is busy updating the index. This can produce sometimes surprising results for users when it simply returns null or throws an error on normal querying operation.
It'd be better to have Hawk simply schedule the query to run later, when the update process has completed.