ceph-volume: fix lvm activate arguments

ceph-volume: fix lvm activate arguments

When using the `lvm activate` subcommand without any osd ID or osd FSID
then ceph-volume fails.

Currently we can either activate with:
 - both osd ID and osd FSID
 - only the osd FSID (because it's unique)

The remaining scenarios aren't covered and generate a stack trace:
 - only the osd ID
 - no osd ID nor osd FSID

This ends up with an error like:

-->  UnboundLocalError: local variable 'tags' referenced before assignment

Fixes: https://tracker.ceph.com/issues/50665
Signed-off-by: Dimitri Savineau <dsavinea@redhat.com>