if the bo shares same reservation object then not lock it again
at swapout time to make it possible to swap out.

v2: refine the commmit message
Reviewed-by: NThomas Hellström <thellstrom@vmware.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Reviewed-by: NChuming Zhou <david1.zhou@amd.com>
Signed-off-by: NRoger He <Hongbo.He@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>