Description of problem:
Failed to unregister system to SAM as "Runtime Error ERROR: update or delete on table "cp_pool" violates foreign key constraint "fk_entitlement_pool" on table "cp_entitlement""

Version-Release number of selected component (if applicable):
SAM-1.4.1-RHEL-6-20141113.0
virt-who-0.16-7.el6.noarch
subscription-manager-1.16.8-8.el6.x86_64
python-rhsm-1.16.6-1.el6.x86_64

How reproducible:
10%

Steps to Reproduce:
1. Register system to SAM1.4.1
2. Subscribe a physical pool "Resilient Storage for Unlimited Guests"
# subscription-manager subscribe --pool=2c90ec8c53c9b0500153c9b2019a0282
Successfully attached a subscription for: Resilient Storage for Unlimited Guests
1 local certificate has been deleted.
3. Unregister system and check rhsm log, please see detail rhsm log in attachment.
# subscription-manager unregister
Runtime Error ERROR: update or delete on table "cp_pool" violates foreign key constraint "fk_entitlement_pool" on table "cp_entitlement"
  Detail: Key (id)=(2c90ec8c53c9b0500153cff55b4a0fbc) is still referenced from table "cp_entitlement". at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse:2,094
# tail -f /var/log/rhsm/rhsm.log
2016-03-31 23:58:38,781 [DEBUG] subscription-manager:24875 @connection.py:557 - Making request: DELETE /sam/api/consumers/1ee3c47f-2585-4346-a3b6-aea321c9716e
2016-03-31 23:58:46,788 [DEBUG] subscription-manager:24875 @connection.py:589 - Response: status=500
2016-03-31 23:58:46,790 [ERROR] subscription-manager:24875 @managercli.py:174 - Unregister failed
2016-03-31 23:58:46,790 [ERROR] subscription-manager:24875 @managercli.py:175 - Runtime Error ERROR: update or delete on table "cp_pool" violates foreign key constraint "fk_entitlement_pool" on table "cp_entitlement"
  Detail: Key (id)=(2c90ec8c53c9b0500153cff55b4a0fbc) is still referenced from table "cp_entitlement". at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse:2,094
Traceback (most recent call last):
  File "/usr/share/rhsm/subscription_manager/managercli.py", line 1268, in _do_command
    managerlib.unregister(self.cp, self.identity.uuid)
  File "/usr/share/rhsm/subscription_manager/managerlib.py", line 792, in unregister
    uep.unregisterConsumer(consumer_uuid)
  File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 1127, in unregisterConsumer
    return self.conn.request_delete(method)
  File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 693, in request_delete
    return self._request("DELETE", method, params)
  File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 598, in _request
    self.validateResponse(result, request_type, handler)
  File "/usr/lib64/python2.6/site-packages/rhsm/connection.py", line 648, in validateResponse
    raise RestlibException(response['status'], error_msg, response.get('headers'))
RestlibException: Runtime Error ERROR: update or delete on table "cp_pool" violates foreign key constraint "fk_entitlement_pool" on table "cp_entitlement"
  Detail: Key (id)=(2c90ec8c53c9b0500153cff55b4a0fbc) is still referenced from table "cp_entitlement". at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse:2,094

Actual results:
Failed to unregister system.

Expected results:
Success to unregister system.

Additional info: