filetop: Fix TypeError by not mixing bytes and str.

When executing the filetop command tool, the following message was
generated:

Traceback (most recent call last):
  File "/usr/share/bcc/tools/filetop", line 190, in <module>
    name = name[:-3] + "..."
TypeError: can't concat bytes to str

Also, by decoding the bytes we print the strings without a leading "b'"
making the output more readable.

tools/filetop.py

@@ -185,14 +185,14 @@ def signal_ignore(signal, frame):
  line = 0
  for k, v in reversed(sorted(counts.items(),
  key=lambda counts: counts[1].rbytes)):
- name = k.name
+ name = k.name.decode()
  if k.name_len > DNAME_INLINE_LEN:
  name = name[:-3] + "..."
 
  # print line
- print("%-6d %-16s %-6d %-6d %-7d %-7d %1s %s" % (k.pid, k.comm,
- v.reads, v.writes, v.rbytes / 1024, v.wbytes / 1024, k.type,
- name))
+ print("%-6d %-16s %-6d %-6d %-7d %-7d %1s %s" % (k.pid,
+ k.comm.decode(), v.reads, v.writes, v.rbytes / 1024,
+ v.wbytes / 1024, k.type.decode(), name))
 
  line += 1
  if line >= maxrows: