update nightly to 2019-05-01 (#4111)

* update nightly to 2019-05-01

* cargo fmt

* cargo fmt

* increase bench timeout

core/src/fullnode.rs

@@ -390,7 +390,6 @@ pub fn make_active_set_entries(
 
 pub fn new_fullnode_for_tests() -> (Fullnode, ContactInfo, Keypair, String) {
     use crate::blocktree::create_new_tmp_ledger;
-    use crate::cluster_info::Node;
 
     let node_keypair = Arc::new(Keypair::new());
     let node = Node::new_localhost_with_pubkey(&node_keypair.pubkey());

core/src/sigverify.rs

@@ -68,9 +68,6 @@ pub fn init() {
 }
 
 fn verify_packet(packet: &Packet) -> u8 {
-    use solana_sdk::pubkey::Pubkey;
-    use solana_sdk::signature::Signature;
-
     let (sig_len, sig_start, msg_start, pubkey_start) = get_packet_offsets(packet, 0);
     let mut sig_start = sig_start as usize;
     let mut pubkey_start = pubkey_start as usize;