=== Split osmo-gbproxy from osmo-sgsn ===

Adjust the build system, packaging etc. to split osmo-gbproxy into its
own git repository. Remove tests and configs that aren't related to
osmo-gbproxy.

Related: OS#4992
diff --git a/contrib/systemd/Makefile.am b/contrib/systemd/Makefile.am
index 11e8f98..81686c1 100644
--- a/contrib/systemd/Makefile.am
+++ b/contrib/systemd/Makefile.am
@@ -1,13 +1,11 @@
 EXTRA_DIST = \
   osmo-gbproxy.service \
-  osmo-gtphub.service \
-  osmo-sgsn.service
+  $(NULL)
 
 if HAVE_SYSTEMD
 SYSTEMD_SERVICES = \
   osmo-gbproxy.service \
-  osmo-gtphub.service \
-  osmo-sgsn.service
+  $(NULL)
 
 systemdsystemunit_DATA = $(SYSTEMD_SERVICES)
 endif