Description of problem:
Hibernate exceptions raised when binding to a pool multiple times in parallel.

Version-Release number of selected component (if applicable):
Candlepin 0.8.15.2

How reproducible:


Steps to Reproduce:
1. Create an owner with 1 entitlement
2. Create multiple consumers
3. Attempt to bind all the consumers to the same entitlement simultaneously

Actual results:
Hibernate exceptions raised. 
Sep 09 03:22:09 [http-8080-6] ERROR org.candlepin.exceptions.mappers.CandlepinExceptionMapper - Runtime Error Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [org.candlepin.model.Pool#8a85f9823e3d5e43013e3e0af77e0f36] at org.hibernate.persister.entity.AbstractEntityPersister.check:1,782

Expected results:
All attempts to bind to the pool are completed successfully up to the quantity of the pool

Additional info:
example script
for i in $(seq 1 16); do ( ssh <host.ip.address$i> "/usr/sbin/subscription-manager attach --pool=<pool_id>"&  ); done;