fix clustersync after node-deletion

fix clustersync after node-deletion

This patch creates the spoolsdirs for a newly joining clusternode on the
master (/var/spool/pmg/cluster/<newnode-cid>/(spam|attachment|virus).

This is necessary in order to prevent a failing cluster-sync for nodes, joining
the cluster after that node has been deleted. (This happens if you remove
a node from the cluster and directly rejoin it to the same masternode):

On the first sync after a node was deleted (there is no section config for a
number < maxcid) each node tries to sync the quarantine for the deleted node
from the cluster (in order to be promotable to new master). This rsync
fails because the spooldir for that node never got created on the master.

The spooldir for a node gets created on the master on the first sync of a node
which can be 2 minutes after joining the cluster (and leaving it again).

Reported via our enterprise support portal.

Signed-off-by: Stoiko Ivanov <s.ivanov@proxmox.com>