Currently, the rpc timeout error for the GOSSIP_GET_ENDPOINT_STATES verb
is not handled in gossiper::do_shadow_round. If the
GOSSIP_GET_ENDPOINT_STATES rpc call to any of the remote nodes goes
timeout, gossiper::do_shadow_round will throw an exception and fail the
whole boot up process.
It is fine that some of the remote nodes timeout in shadow round. It is
not a must to talk to all nodes.
This patch fixes an issue we saw recently in our sct tests:
```
INFO | scylla[1579]: [shard 0] init - Shutting down gossiping
INFO | scylla[1579]: [shard 0] gossip - gossip is already stopped
INFO | scylla[1579]: [shard 0] init - Shutting down gossiping was successful
...
ERR | scylla[1579]: [shard 0] init - Startup failed: seastar::rpc::timeout_error (rpc call timed out)
```
Fixes#8187Closes#8213
dc40184faa