Configure PcapRecorder to record on any iface

Before this commit, tcpdump was instructed to listen only on the
interface which had the IP assigned. However, local processes connecting
to that IP are actually sending packets through the loopback interface.
As we are not listening on it, all those packets are not being recorded.
Let's record on all interfaces instead and rely on the ip filtering to
record only the interesting packets.

Change-Id: I205786d5168acd66cf3427154d8bf307c5c58da5
diff --git a/src/osmo_gsm_tester/osmo_nitb.py b/src/osmo_gsm_tester/osmo_nitb.py
index b0a706d..6dd7342 100644
--- a/src/osmo_gsm_tester/osmo_nitb.py
+++ b/src/osmo_gsm_tester/osmo_nitb.py
@@ -52,8 +52,7 @@
         if not os.path.isdir(lib):
             raise RuntimeError('No lib/ in %r' % inst)
 
-        iface = util.ip_to_iface(self.addr())
-        pcap_recorder.PcapRecorder(self.suite_run, self.run_dir.new_dir('pcap'), iface,
+        pcap_recorder.PcapRecorder(self.suite_run, self.run_dir.new_dir('pcap'), None,
                                    'host %s and port not 22' % self.addr())
 
         env = { 'LD_LIBRARY_PATH': util.prepend_library_path(lib) }