Storage motion changes. Incorporated the review comments.
1. Introduced a new XenServerStorageMotionStrategy for migrating volumes of a vm. When a vm is being migrated with its volumes, the vm is put in migrating state and a request is send to the volume manager to migrate the vm and its volumes. Volume manager calls into the volume service which forwards the request to data motion service after moving all the volumes to migrating state. Data motion service enumerates the strategies and the request reaches the XenServerStorageMotionStrategy. It calls in to the resource to complete the operation.
2. Removed migrateAsync from data motion service. The work of migrating a volume of a running vm is also done in copyAsync.
3. Fixed the marvin test scripts that were affected by renaming list apis to find apis.