test: Fix intermittent issue in p2p_handshake.py

If we reuse the same port when disconnecting and establishing connections
again, we might hit this scenario:
- disconnection is done on python side for P2PConnection
- disconnection is not complete on c++ side for TestNode
- we're trying to establish a new connection on same port again

Prevent this scenario from happening by using a different p2p_idx/port
everytime.

Author: stratospher

test/functional/p2p_handshake.py

@@ -31,9 +31,9 @@ class P2PHandshakeTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
 
-    def add_outbound_connection(self, node, connection_type, services, wait_for_disconnect):
+    def add_outbound_connection(self, node, peer_id, connection_type, services, wait_for_disconnect):
         peer = node.add_outbound_p2p_connection(
-            P2PInterface(), p2p_idx=0, wait_for_disconnect=wait_for_disconnect,
+            P2PInterface(), p2p_idx=peer_id, wait_for_disconnect=wait_for_disconnect,
             connection_type=connection_type, services=services,
             supports_v2_p2p=self.options.v2transport, advertise_v2_p2p=self.options.v2transport)
         if not wait_for_disconnect:
@@ -47,6 +47,7 @@ def test_desirable_service_flags(self, node, service_flag_tests, desirable_servi
            service flags in the VERSION message. The test is exercised for all relevant
            outbound connection types where the desirable service flags check is done."""
         CONNECTION_TYPES = ["outbound-full-relay", "block-relay-only", "addr-fetch"]
+        peer_id = 0
         for conn_type, services in itertools.product(CONNECTION_TYPES, service_flag_tests):
             if self.options.v2transport:
                 services |= NODE_P2P_V2
@@ -57,10 +58,11 @@ def test_desirable_service_flags(self, node, service_flag_tests, desirable_servi
                 expected_debug_log = f'does not offer the expected services ' \
                         f'({services:08x} offered, {desirable_service_flags:08x} expected)'
                 with node.assert_debug_log([expected_debug_log]):
-                    self.add_outbound_connection(node, conn_type, services, wait_for_disconnect=True)
+                    self.add_outbound_connection(node, peer_id, conn_type, services, wait_for_disconnect=True)
             else:
                 assert (services & desirable_service_flags) == desirable_service_flags
-                self.add_outbound_connection(node, conn_type, services, wait_for_disconnect=False)
+                self.add_outbound_connection(node, peer_id, conn_type, services, wait_for_disconnect=False)
+            peer_id += 1
 
     def generate_at_mocktime(self, time):
         self.nodes[0].setmocktime(time)
@@ -85,7 +87,7 @@ def run_test(self):
 
         self.log.info("Check that feeler connections get disconnected immediately")
         with node.assert_debug_log([f"feeler connection completed"]):
-            self.add_outbound_connection(node, "feeler", NODE_NONE, wait_for_disconnect=True)
+            self.add_outbound_connection(node, 0, "feeler", NODE_NONE, wait_for_disconnect=True)
 
 
 if __name__ == '__main__':