Fix folding option
Fix folding option

Using the "folding" option produces an error.

/usr/share/bcc/tools/offwaketime -f 3 > out.stacks

Traceback (most recent call last):
  File "/usr/share/bcc/tools/offwaketime", line 305, in <module>
    print("%s %d" % (str.join(";", line), v.value))
TypeError: sequence item 0: expected str instance, bytes found

It seems that k.target and k.waker are always type = bytes.  This edit resolves this error.
Thank you for your time.
iovisor/bcc,brendangregg/bcc,tuxology/bcc,brendangregg/bcc,iovisor/bcc,mcaleavya/bcc,iovisor/bcc,mcaleavya/bcc,tuxology/bcc,mcaleavya/bcc,tuxology/bcc,brendangregg/bcc,brendangregg/bcc,mcaleavya/bcc,tuxology/bcc,brendangregg/bcc,mcaleavya/bcc,iovisor/bcc,tuxology/bcc,iovisor/bcc