close #2792: allow online migration with replicated snapshots

close #2792: allow online migration with replicated snapshots

Since commit 9b6efe43 ("migrate: add live-migration of replicated
disks") live-migration with replicated volumes is possible. When
handling the replication, it is checked that all local volumes
previously detected as replicatable are actually replicated. So the
check if migration with snapshots is possible can just allow volumes
that are detected as replicatable.

Note that VM state files are also replicated.

If there is an invalid configuration with a non-replicatable volume or
state file and replication is enabled, then replication will fail, and
thus migration will fail early.

Trying to live-migrate to a non-replication target (needs --force)
will still fail if there are snapshots, because they are (correctly)
detected as non-replicated.

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