Description of problem:

When user performs a "Change CD" operation on running VM a java ExecutionException appears in log and the desired operation is not completed and rolls back.

Version-Release number of selected component (if applicable):
ovirt-engine-restapi-3.0.0_0001-7.fc16.x86_64
ovirt-engine-webadmin-portal-3.0.0_0001-7.fc16.x86_64
ovirt-engine-dbscripts-3.0.0_0001-7.fc16.x86_64
ovirt-engine-backend-3.0.0_0001-7.fc16.x86_64
ovirt-engine-setup-3.0.0_0001-7.fc16.x86_64
ovirt-engine-3.0.0_0001-7.fc16.x86_64
ovirt-engine-config-3.0.0_0001-7.fc16.x86_64
ovirt-engine-jbossas-1-1.fc16.x86_64
ovirt-engine-jboss-deps-3.0.0_0001-7.fc16.x86_64
ovirt-engine-userportal-3.0.0_0001-7.fc16.x86_64
ovirt-engine-genericapi-3.0.0_0001-7.fc16.x86_64
ovirt-engine-notification-service-3.0.0_0001-7.fc16.x86_64
ovirt-engine-log-collector-3.0.0_0001-7.fc16.x86_64
ovirt-engine-iso-uploader-3.0.0_0001-7.fc16.x86_64
ovirt-engine-tools-common-3.0.0_0001-7.fc16.x86_64

How reproducible:
100 %

Steps to Reproduce:
1. Create a vm
2. Run the vm from step #1
3. Try to Change CD
  
Actual results:
Operation fails with java exception

Expected results:
CD should be changed to the vm and user should be able to use it

Additional info: LOG:

2012-01-16 13:30:10,276 INFO  [org.ovirt.engine.core.vdsbroker.irsbroker.IsoPrefixVDSCommand] (http-0.0.0.0-8080-4) START, IsoPrefixVDSCommand(storagePoolId = f6478fa6-3dcf-11e1-84d9-471d3d1ae878, ignoreFailoverLimit = false, compatabilityVersion = null), log id: 1b6237b2
2012-01-16 13:30:10,276 INFO  [org.ovirt.engine.core.vdsbroker.irsbroker.IsoPrefixVDSCommand] (http-0.0.0.0-8080-4) FINISH, IsoPrefixVDSCommand, return: /rhev/data-center/f6478fa6-3dcf-11e1-84d9-471d3d1ae878/f1621233-13f4-4c6b-99e3-86fbd4dbdad2/images/11111111-1111-1111-1111-111111111111, log id: 1b6237b2
2012-01-16 13:30:10,305 INFO  [org.ovirt.engine.core.bll.ChangeDiskCommand] (http-0.0.0.0-8080-4) Running command: ChangeDiskCommand internal: false. Entities affected :  ID: 00c73e31-27e1-42b0-8424-de74ca121797 Type: VM
2012-01-16 13:30:10,310 INFO  [org.ovirt.engine.core.vdsbroker.vdsbroker.ChangeDiskVDSCommand] (http-0.0.0.0-8080-4) START, ChangeDiskVDSCommand(vdsId = 13300352-4026-11e1-83c5-cfccd7b92465, vmId=00c73e31-27e1-42b0-8424-de74ca121797, diskPath=/rhev/data-center/f6478fa6-3dcf-11e1-84d9-471d3d1ae878/f1621233-13f4-4c6b-99e3-86fbd4dbdad2/images/11111111-1111-1111-1111-111111111111/RHEV-toolsSetup_2.2_52832.iso), log id: 4b5f1e04
2012-01-16 13:30:10,348 ERROR [org.ovirt.engine.core.vdsbroker.vdsbroker.VdsBrokerCommand] (http-0.0.0.0-8080-4) XML RPC error in command ChangeDiskVDS ( Vds: 10.34.63.207 ), the error was: java.util.concurrent.ExecutionException: java.lang.reflect.InvocationTargetException 
2012-01-16 13:30:10,349 INFO  [org.ovirt.engine.core.vdsbroker.vdsbroker.ChangeDiskVDSCommand] (http-0.0.0.0-8080-4) FINISH, ChangeDiskVDSCommand, log id: 4b5f1e04
2012-01-16 13:30:10,349 ERROR [org.ovirt.engine.core.bll.ChangeDiskCommand] (http-0.0.0.0-8080-4) Command org.ovirt.engine.core.bll.ChangeDiskCommand throw Vdc Bll exception. With error message VdcBLLException: org.ovirt.engine.core.vdsbroker.vdsbroker.VDSNetworkException: VDSNetworkException: 
2012-01-16 13:30:10,353 ERROR [org.ovirt.engine.core.bll.ChangeDiskCommand] (http-0.0.0.0-8080-4) Transaction rolled-back for command: org.ovirt.engine.core.bll.ChangeDiskCommand.