zbwireshark: adjust arguments to subprocess.Popen() depending on OS
zbwireshark: adjust arguments to subprocess.Popen() depending on OS

os.setpgrp() only exists on *nix. On Windows, we can actually Ctrl+C the
script in the console and Wireshark will stay open. However, it seems like
a good idea to still put the process in a separate process group, so we
do that with creationflags on Windows.

rfmcpherson/killerbee,Crypt0s/killerbee,Crypt0s/killerbee,Crypt0s/killerbee,Crypt0s/killerbee,rfmcpherson/killerbee,rfmcpherson/killerbee,rfmcpherson/killerbee