storage/lvm: make sure volume cache is refreshed after changes
storage/lvm: make sure volume cache is refreshed after changes

Even if start/stop fails, still refresh the cache. The failed operation
might still modified something.

marmarek/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin