Fix bugs if stopping sendpfast via Ctrl+C (secdev#4690)

* Fix bugs if stopping sendpfast via Ctrl+C

Author: badcodebuilder

scapy/sendrecv.py

@@ -586,11 +586,13 @@ def sendpfast(x: _PacketIterable,
             cmd = subprocess.Popen(argv, stdout=subprocess.PIPE,
                                    stderr=subprocess.PIPE)
         except KeyboardInterrupt:
+            if cmd:
+                cmd.terminate()
             log_interactive.info("Interrupted by user")
         except Exception:
             os.unlink(f)
             raise
-        else:
+        finally:
             stdout, stderr = cmd.communicate()
             if stderr:
                 log_runtime.warning(stderr.decode())