lvm: wipe signatures on lvcreate

lvm: wipe signatures on lvcreate

With PVE 7.0 we use upstream's lvm2 packages, which seem to detect
'more' signatures (and refuse creating lvs when they are present)

This prevents creating new disks on LVM (thick) storages as reported
on pve-user [0].

Adding -Wy to wipe signatures, and --yes (to actually wipe them
instead of prompting) fixes the aborted lvcreate.

Adding only to LVMPlugin and not to the lvcreate calls in
LvmThinPlugin, since I assume (and my quick tests confirm) that thin
pools are not affected by this issue..

Tested on a virtual test-setup with a LVM storage on a (virtual) iscsi
target and a local lvmthin storage.

[0] https://lists.proxmox.com/pipermail/pve-user/2021-July/172660.html

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>