Using foreman 1.5 and ovirt 3.4.1, I have similar issues. When creating the VM, it fails. But the vm has been created without a disk. The strange thing is the error talks a about "Cannot remove VM" while it's a newly created VM:

Unable to save
Failed to destroy a compute xxxxxxx (oVirt) instance test2.xxx.xxx: Cannot remove VM: The following disks are locked: test2-xxx-xxx_Disk1. Please try again in a few minutes.
mac value is blank!
Failed to destroy a compute xxxxxxx (oVirt) instance test2.xxx.xxx: Cannot remove VM: The following disks are locked: test2-xxx-xxx_Disk1. Please try again in a few minutes.

From the ovirt log:

2014-05-19 13:47:02,744 INFO [org.ovirt.engine.core.bll.AddDiskCommand] (ajp--127.0.0.1-8702-6) [2b8cb67e] Running command: AddDiskCommand internal: false. Entities affected : ID: e1a787a6-c4ce-4e72-8d69-3beb6abc3e8b Type: VM, ID: 0751cdb1-0ee3-494c-88e2-c0e7df58aa52 Type: Storage
2014-05-19 13:47:02,744 INFO [org.ovirt.engine.core.bll.ImagesHandler] (ajp--127.0.0.1-8702-6) [2b8cb67e] Disk alias retrieved from the client is null or empty, the suggested default disk alias to be used is test2-xxxx-xxx_Disk1
2014-05-19 13:47:02,955 INFO [org.ovirt.engine.core.bll.AddImageFromScratchCommand] (ajp--127.0.0.1-8702-6) [70732b8f] Running command: AddImageFromScratchCommand internal: true. Entities affected : ID: 0751cdb1-0ee3-494c-88e2-c0e7df58aa52 Type: Storage
2014-05-19 13:47:02,977 INFO [org.ovirt.engine.core.bll.AddImageFromScratchCommand] (ajp--127.0.0.1-8702-6) [70732b8f] Lock freed to object EngineLock [exclusiveLocks= , sharedLocks= key: e1a787a6-c4ce-4e72-8d69-3beb6abc3e8b value: VM
]
2014-05-19 13:47:02,978 INFO [org.ovirt.engine.core.vdsbroker.irsbroker.CreateImageVDSCommand] (ajp--127.0.0.1-8702-6) [70732b8f] START, CreateImageVDSCommand( storagePoolId = 00000002-0002-0002-0002-000000000390, ignoreFailoverLimit = false, storageDomainId = 0751cdb1-0ee3-494c-88e2-c0e7df58aa52, imageGroupId = 395e6b7b-a34c-4c06-9e0f-83e0a9dde925, imageSizeInBytes = 53687091200, volumeFormat = COW, newImageId = 450c6f08-d658-4468-b2d4-845d1eae6013, newImageDescription = ), log id: 75e5e9dd
2014-05-19 13:47:02,979 INFO [org.ovirt.engine.core.vdsbroker.irsbroker.CreateImageVDSCommand] (ajp--127.0.0.1-8702-6) [70732b8f] -- executeIrsBrokerCommand: calling 'createVolume' with two new parameters: description and UUID
2014-05-19 13:47:03,378 INFO [org.ovirt.engine.core.vdsbroker.irsbroker.CreateImageVDSCommand] (ajp--127.0.0.1-8702-6) [70732b8f] FINISH, CreateImageVDSCommand, return: 450c6f08-d658-4468-b2d4-845d1eae6013, log id: 75e5e9dd
2014-05-19 13:47:03,408 INFO [org.ovirt.engine.core.bll.CommandAsyncTask] (ajp--127.0.0.1-8702-6) [70732b8f] CommandAsyncTask::Adding CommandMultiAsyncTasks object for command 7cf949b8-d057-49a4-867f-0ec64ed6c815
2014-05-19 13:47:03,408 INFO [org.ovirt.engine.core.bll.CommandMultiAsyncTasks] (ajp--127.0.0.1-8702-6) [70732b8f] CommandMultiAsyncTasks::AttachTask: Attaching task c64e4721-0a7e-4448-8770-b089b8557ad4 to command 7cf949b8-d057-49a4-867f-0ec64ed6c815.
2014-05-19 13:47:03,444 INFO [org.ovirt.engine.core.bll.AsyncTaskManager] (ajp--127.0.0.1-8702-6) [70732b8f] Adding task c64e4721-0a7e-4448-8770-b089b8557ad4 (Parent Command AddDisk, Parameters Type org.ovirt.engine.core.common.asynctasks.AsyncTaskParameters), polling hasn't started yet..
2014-05-19 13:47:03,544 INFO [org.ovirt.engine.core.dal.dbbroker.auditloghandling.AuditLogDirector] (ajp--127.0.0.1-8702-6) [70732b8f] Correlation ID: 2b8cb67e, Job ID: c364dfa5-198c-4bc4-a725-2878e2743e42, Call Stack: null, Custom Event ID: -1, Message: Add-Disk operation of test2-netbulae-mgmt_Disk1 was initiated on VM test2-netbulae-mgmt by admin.
2014-05-19 13:47:03,546 INFO [org.ovirt.engine.core.bll.SPMAsyncTask] (ajp--127.0.0.1-8702-6) [70732b8f] BaseAsyncTask::startPollingTask: Starting to poll task c64e4721-0a7e-4448-8770-b089b8557ad4.

2014-05-19 13:47:04,113 INFO [org.ovirt.engine.core.bll.RemoveVmCommand] (ajp--127.0.0.1-8702-9) [5f576a1b] Lock Acquired to object EngineLock [exclusiveLocks= key: e1a787a6-c4ce-4e72-8d69-3beb6abc3e8b value: VM
, sharedLocks= ]
2014-05-19 13:47:04,119 WARN [org.ovirt.engine.core.bll.RemoveVmCommand] (ajp--127.0.0.1-8702-9) [5f576a1b] CanDoAction of action RemoveVm failed. Reasons:VAR__ACTION__REMOVE,VAR__TYPE__VM,ACTION_TYPE_FAILED_DISKS_LOCKED,$diskAliases test2-xxxxx-xxx_Disk1
2014-05-19 13:47:04,120 INFO [org.ovirt.engine.core.bll.RemoveVmCommand] (ajp--127.0.0.1-8702-9) [5f576a1b] Lock freed to object EngineLock [exclusiveLocks= key: e1a787a6-c4ce-4e72-8d69-3beb6abc3e8b value: VM
, sharedLocks= ]
2014-05-19 13:47:04,144 ERROR [org.ovirt.engine.api.restapi.resource.AbstractBackendResource] (ajp--127.0.0.1-8702-9) Operation Failed: [Cannot remove VM: The following disks are locked: test2-xxxxx-xxx_Disk1. Please try again in a few minutes.]