netinet tests: only log critical errors from scapy

See also a26e895f3d.

MFC after:	1 week
Sponsored by:	Rubicon Communications, LLC ("Netgate")

tests/sys/netinet/redirect.py

@@ -29,6 +29,8 @@
 #
 
 import argparse
+import logging
+logging.getLogger("scapy").setLevel(logging.CRITICAL)
 import scapy.all as sc
 import socket
 import sys