p2p: Ignore version msgs after initial version msg

Sending a version message after the intial version message is peer
misbehavior. Though, it seems arbitrary and confusing to disconnect only
after exactly 100 version messages. Duplicate version messages affect us
no different than any other unknown message. So remove the Misbehaving
and ignore the redundant msgs.

test/functional/p2p_invalid_messages.py

@@ -18,6 +18,7 @@ from test_framework.messages import (
     msg_inv,
     msg_ping,
     MSG_TX,
+    msg_version,
     ser_string,
 )
 from test_framework.p2p import (
@@ -60,6 +61,7 @@ class InvalidMessagesTest(BitcoinTestFramework):
 
     def run_test(self):
         self.test_buffer()
+        self.test_duplicate_version_msg()
         self.test_magic_bytes()
         self.test_checksum()
         self.test_size()
@@ -92,6 +94,13 @@ class InvalidMessagesTest(BitcoinTestFramework):
         conn.sync_with_ping(timeout=1)
         self.nodes[0].disconnect_p2ps()
 
+    def test_duplicate_version_msg(self):
+        self.log.info("Test duplicate version message is ignored")
+        conn = self.nodes[0].add_p2p_connection(P2PDataStore())
+        with self.nodes[0].assert_debug_log(['redundant version message from peer']):
+            conn.send_and_ping(msg_version())
+        self.nodes[0].disconnect_p2ps()
+
     def test_magic_bytes(self):
         self.log.info("Test message with invalid magic bytes disconnects peer")
         conn = self.nodes[0].add_p2p_connection(P2PDataStore())