Add function volume_snapshot_delete_remote.

This function we need for replica to handle snapshots on remote nodes.

PVE/Storage/Plugin.pm

@@ -725,6 +725,13 @@ sub volume_snapshot_rollback {
     return undef;
 }
 
+sub volume_snapshot_delete_remote {
+    my ($class, $scfg, $storeid, $volname, $snap, $ip) = @_;
+
+    # implement in subclass
+    die "Volume_snapshot_delete_remote is not implemented for $class";
+}
+
 sub volume_snapshot_delete {
     my ($class, $scfg, $storeid, $volname, $snap, $running) = @_;