[nova]The code about BP Allow migrating PMEM's dat

Hi all: Is there anything in the code logic that needs to be modified? If there is no problem with the implementation structure of the code, I start adding unit tests. https://review.opendev.org/c/openstack/nova/+/802225 Thank you Fossen. --------------------------------- Fossen Qiu | 邱军婷 CBRD | 云计算与大数据研发部 T: 18249256272 E: qiujunting@inspur.com<mailto:qiujunting@inspur.com> 浪潮云海