RHEV reports that the export domain requires cleaning

Issue

When attempting to create an export domain in a data center, the following error shows up in /var/log/ovirt-engine/engine.log:

2013-09-20 14:51:25,822 INFO  [org.ovirt.engine.core.vdsbroker.vdsbroker.BrokerCommandBase] (ajp-/127.0.0.1:8702-7) [7b5a037] Command org.ovirt.engine.core.vdsbroker.vdsbroker.CreateStorageDomainVDSCommand return value 
 Class Name: org.ovirt.engine.core.vdsbroker.vdsbroker.StatusOnlyReturnForXmlRpc
mStatus                       Class Name: org.ovirt.engine.core.vdsbroker.vdsbroker.StatusForXmlRpc
mCode                         361
mMessage                      Storage domain is not empty - requires cleaning: ('rhevm.codelpa.dom:/export/export',)