bts/osmo-bts.cfg: enable GSMTAP Um frame logging

Change-Id: Icc5ffed6cda47c15ac703ef336ef502d2047cc2c
diff --git a/bts/osmo-bts.cfg b/bts/osmo-bts.cfg
index 0db4305..1c83db7 100644
--- a/bts/osmo-bts.cfg
+++ b/bts/osmo-bts.cfg
@@ -51,6 +51,7 @@
  rtp jitter-buffer 100
  paging queue-size 200
  paging lifetime 0
+ gsmtap-remote-host 127.0.0.1
  gsmtap-sapi enable-all
  no gsmtap-sapi pdtch
  no gsmtap-sapi ptcch