Garbage collection to be run by cron job

In 3.1, 3.2, garbage collection is triggered when the user make a reservation and the license is full. the GC process should take about 400ms for each request which is quite huge. 
When it's come to process-based floating license, with the high load of request and license needed, the pool easily become full and garbage collect might be one blocker to stop the process.
Solution: Study if we can remove the GC from the license reservation process and instead using cronjob to run the GC