Restart node test (#3459) (#3465)

* Restart node test (#3459)

* Add test to local_cluster for restarting a node

* fix so that we don't hit end of epoch - leader not found before trying to transfer

* Do not look for confirmations, b/c nobody is voting on empty transmissions in this single node test

core/src/cluster.rs

@@ -0,0 +1,6 @@
+use solana_sdk::pubkey::Pubkey;
+
+pub trait Cluster {
+    fn get_node_ids(&self) -> Vec<Pubkey>;
+    fn restart_node(&mut self, pubkey: Pubkey);
+}