Fix flaky tests by waiting for test node to boot (#3845)

core/src/fullnode.rs

@@ -8,7 +8,7 @@ use crate::contact_info::ContactInfo;
 use crate::entry::create_ticks;
 use crate::entry::next_entry_mut;
 use crate::entry::Entry;
-use crate::gossip_service::GossipService;
+use crate::gossip_service::{discover_nodes, GossipService};
 use crate::leader_schedule_utils;
 use crate::poh_recorder::PohRecorder;
 use crate::poh_service::{PohService, PohServiceConfig};
@@ -395,7 +395,7 @@ pub fn new_fullnode_for_tests() -> (Fullnode, ContactInfo, Keypair, String) {
         None,
         &FullnodeConfig::default(),
     );
-
+    discover_nodes(&contact_info.gossip, 1).expect("Node startup failed");
     (node, contact_info, mint_keypair, ledger_path)
 }