gossip: Do not print node is now part of the cluster during gossip shadow round
gossip: Do not print node is now part of the cluster during gossip shadow round

With

   Node 1 (Seed node, Port 7000 is opened, 10.184.9.144)
   Node 2 (Port 7000 is opened, 10.184.9.145)
   Node 3 (Port 7000 is blocked by firewall)

On Node 3, we saw the following error which was very confusing: Node 3
saw Node 1 and Node 3 but it complained it can not contact any seeds.

The message "Node 10.184.9.144 is now part of the cluster" and friends
are actually messages printed during the gossip shadow round where Node
3 connects to Node 1's port 7000 and Node 1 returns all info it knows to
Node 3, so that Node 3 knows Node 1 and Node 2 and we see the "Node
10.184.9.144/145 is now part of the cluster" message.

However, during the normal gossip round, Node 3 will not mark Node 1 and
Node 2 UP until the Seed node initiates a gossip round to Node 3, (note
port 7000 on node 3 is blocked in this case). So Node 3 will not mark
Node 1 and Node 2 UP and we see the "Unable to contact any seeds" error.

[shard 0] storage_service - Loading persisted ring state
[shard 0] gossip - Node 10.184.9.144 is now part of the cluster
[shard 0] gossip - inet_address 10.184.9.144 is now UP
[shard 0] gossip - Node 10.184.9.145 is now part of the cluster
[shard 0] gossip - inet_address 10.184.9.145 is now UP
[shard 0] storage_service - Starting up server gossip
scylla_run[12479]: Start gossiper service ...
[shard 0] storage_service - JOINING: waiting for ring information
[shard 0] storage_service - JOINING: schema complete, ready to bootstrap
[shard 0] storage_service - JOINING: waiting for pending range calculation
[shard 0] storage_service - JOINING: calculation complete, ready to bootstrap
[shard 0] storage_service - JOINING: getting bootstrap token
[shard 0] storage_service - JOINING: sleeping 5000 ms for pending range setup
scylla_run[12479]: Exiting on unhandled exception of type 'std::runtime_error': Unable to contact any seeds!

duarten/scylla,kjniemi/scylla,kjniemi/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,kjniemi/scylla,avikivity/scylla,raphaelsc/scylla,scylladb/scylla,raphaelsc/scylla,scylladb/scylla,duarten/scylla,duarten/scylla,avikivity/scylla,raphaelsc/scylla