In the current implementation when GRAM client delegates the credentials to 
the delgation service. it can use the delagated credentials to submit multiple 
jobs. This feature increase the performance for submitting multiple jobs by 
the same user. Similarly if the same user wants to submit more jobs in another 
process he cannot use the same delgated credentials. It would be really useful 
if he could query that delgated credentials exist then he uses existing 
credentials otherwise submit new credentials. This would have following 
benefits.
 - Overhead associated with credential renewal will be less.
 - User can now submit multiple credentials with different policies. He could 
now permit another user to use one of the delgated credentials. He could have 
different policies for different credentials.