lvm thin: don't assume that a thin pool and its volumes are active

lvm thin: don't assume that a thin pool and its volumes are active

There are cases where autoactivation can fail, as reported in the
community forum [0]. And it could also be that a volume was
deactivated by something outside of our control.

It doesn't seem strictly necessary to activate the thin pool itself
(creating/removing/activating LVs within the pool still works if it's
not active), but it does not report usage information as long as
neither the pool nor any of its LVs are active. Activate the pool for
that, for being able to use the flag in status(), and it should also
serve as a good indicator that there's a problem with the pool if it
can't be activated.

Before activating, check the (cached) lv_state from lvm_list_volumes.
It's necessary to update the cache in activate_storage, because the
flag is re-used in status(). Also update it for other (de)activations
to be more future-proof.

[0]: https://forum.proxmox.com/threads/local-lvm-not-available-after-kernel-update-on-pve-7.97406

Signed-off-by: Fabian Ebner <f.ebner@proxmox.com>