Agent: Fix error when shutting down sockets in _check_tcp_ports()

An error is raised if shutdown() is called on a socket that has not
successfully connected. This commit modifies the cleanup logic so that
shutdown() is only called on sockets that are known to be connected and
close() is called on all sockets.

monkey/infection_monkey/network/tcp_scanner.py

@@ -1,7 +1,7 @@
 import logging
 import select
 import socket
-from typing import Iterable, Mapping
+from typing import Iterable, Mapping, Tuple
 
 from infection_monkey.i_puppet import PortScanData, PortStatus
 from infection_monkey.network.tools import BANNER_READ, DEFAULT_TIMEOUT, tcp_port_to_service
@@ -113,13 +113,28 @@ def _check_tcp_ports(
                     else:
                         open_ports[port] = ""
 
-            # try to cleanup
-            for s in possible_ports:
-                s[1].shutdown(socket.SHUT_RDWR)
-                s[1].close()
-
     except socket.error as exc:
         logger.warning("Exception when checking ports on host %s, Exception: %s", str(ip), exc)
 
-    finally:
-        return open_ports
+    _clean_up_sockets(possible_ports, connected_ports_sockets)
+
+    return open_ports
+
+
+def _clean_up_sockets(
+    possible_ports: Iterable[Tuple[int, socket.socket]],
+    connected_ports_sockets: Iterable[Tuple[int, socket.socket]],
+):
+    # Only call shutdown() on sockets we know to be connected
+    for port, s in connected_ports_sockets:
+        try:
+            s.shutdown(socket.SHUT_RDWR)
+        except socket.error as exc:
+            logger.warning(f"Error occurred while shutting down socket on port {port}: {exc}")
+
+    # Call close() for all sockets
+    for port, s in possible_ports:
+        try:
+            s.close()
+        except socket.error as exc:
+            logger.warning(f"Error occurred while closing socket on port {port}: {exc}")