tools/ctdb: Fix arguments/semantics of rebalance node
There's no reason why specifying a node should be compulsory. This is
a cluster-wide operation because it is implemented by the recovery
master so multiple nodes should not be specified using -n. However,
the command should be able to specify multiple nodes so let it have
its own nodestring argument.
This change should be backward compatible with the old requirement of
specifying a single node via -n.
Signed-off-by: Martin Schwenke <martin@meltin.net>
(This used to be ctdb commit
0846c00597adb66bba8c9dbf63443d0c2f91a7d1)