ctdb-common: Do not queue a packet if queue does not have valid fd

ctdb-common: Do not queue a packet if queue does not have valid fd

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13056

The only time a ctdb_queue is created without valid fd is when CTDB
is trying to establish connections with other nodes in the cluster.
All the other uses always create a ctdb_queue with valid fd.

This avoids queueing up packets for dead nodes or nodes that are not
running in the cluster and stops consuming memory.

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Martin Schwenke <martin@meltin.net>