Misc fixes on Python tools (#2136)

Misc fixes on Python tools
diff --git a/tools/filetop.py b/tools/filetop.py
index e9f67a2..91e098e 100755
--- a/tools/filetop.py
+++ b/tools/filetop.py
@@ -60,7 +60,7 @@
 loadavg = "/proc/loadavg"
 
 # signal handler
-def signal_ignore(signal, frame):
+def signal_ignore(signal_value, frame):
     print()
 
 # define BPF program