Fixes bug 1040332.
Xapi VM.migrate_send and VM.assert_can_migrate calls require that
vdi_map parameter is a (source_vdi_ref -> target_sr_ref) mapping, for block
live migration to work, as of XenServer 6.0 RC1.
On the destination side:
This fix modifies the check_can_live_migrate_destination call, so that the
value returned contains the "destination_sr_ref" (XenAPI specific data is
stored under the "migrate_send_data key").
On the source side:
check_can_live_migrate_source and live_migrate calls assemble the
vdi_map by mapping all the local sr contained vdis of the VM to
destination_sr_ref, and passing this parameter to the VM.migrate_send and
VM.assert_can_migrate Xapi calls.
Change-Id: I95f3dca651d2e72fc727646580092a25f558d6ba