gstlal: add temporary package conflict

- the newly resurrected stock python plugin loader induces segfaults in gstlal if the two are installed together, and there is no work-around.  we will be transitioning to the stock loader for O3 but for the time-being we need to add the conflict to the package data to prevent breakage.

gstlal/debian/control.in

@@ -65,6 +65,8 @@ Depends: ${shlibs:Depends}, ${misc:Depends}, ${python:Depends},
  python-gst-1.0,
  python-numpy,
  python-scipy
+Conflicts:
+ gstreamer1.0-python3-plugin-loader
 Description: GStreamer for GW data analysis (core stable parts)
  This package provides a variety of GStreamer elements for
  gravitational-wave data analysis and some libraries to help write such