When the test VM is accidentally rebooted, there exists the previously
created volume, and the command fails with the following:
```
TEST-64-UDEV-STORAGE.sh[282]: + lvm pvcreate -y /dev/md/mdlvm
TEST-64-UDEV-STORAGE.sh[442]: Can't initialize physical volume "/dev/md127" of volume group "mdlvm_vg" without -ff
TEST-64-UDEV-STORAGE.sh[442]: /dev/md127: physical volume not initialized.
[FAILED] Failed to start TEST-64-UDEV-STORAGE-mdadm_lvm.service.
```
Let's ignore the existence of previous volume and forcibly create new one.
Workaround for issue #38240.
Yu Watanabe
8685f8edd1