Optimizing List Objects by using binary sort to discard entries in cases
where prefix or marker is set.
Adding test coverage to ListObjects.
Adding benchmark to ListObjects.
When list object is invoked, it creates a goroutine if not available
for given parameters else uses existing goroutine. These goroutines
are alive for 15 seconds for further continuation list object request
else they exit.
Fixes#1076
Harshavardhana