NEEDS PROPER EXCEPTION CA-143836: Add VDI.revert API call

Signed-off-by: John Else <john.else@citrix.com>
Enable vdi_revert as SM op

Signed-off-by: John Else <john.else@citrix.com>
DRAFT allow VDI.revert operation

Signed-off-by: John Else <john.else@citrix.com>