Storage: Use storaged instead of patched UDisks2.

Closes: #190

Signed-off-by: Stef Walter <stefw@redhat.com>
Storage: Skip pools when walking a volume group.

They might or might not have block devices associated with them, but
we never want to clean them up or check whether they are unused.

Signed-off-by: Stef Walter <stefw@redhat.com>
Storage: Handle active volumes without block devices.

And show them as "unsupported".  This is better than showing them
erroneously as "inactive".

See https://bugs.freedesktop.org/show_bug.cgi?id=73731

Signed-off-by: Stef Walter <stefw@redhat.com>