Add sys.stdout.flush() during print (iovisor#5142)

without that, pipe doesn't work well because of buffer

Author: ikicha

tools/tcpstates.py

@@ -19,6 +19,7 @@
 from bcc import BPF
 import argparse
 from socket import inet_ntop, AF_INET, AF_INET6
+import sys
 from time import strftime, time
 from os import getuid
 
@@ -434,6 +435,7 @@ def print_ipv6_event(cpu, data, size):
 b["ipv6_events"].open_perf_buffer(print_ipv6_event, page_cnt=64)
 while 1:
     try:
+        sys.stdout.flush()
         b.perf_buffer_poll()
     except KeyboardInterrupt:
         exit()