disable system bus tests for now

because they do not work when building RPMs in OBS

To be replaced by session bus tests where we tell limited-session-bus.conf to
disallow some names.

spec/bus_connection_spec.rb

@@ -38,7 +38,7 @@
 
     context "when we're not allowed to own the name", tag_system_bus: true do
       let(:bus) { DBus::ASystemBus.new }
-      it "raises an error... too late" do
+      xit "raises an error... too late" do
         name = "org.rubygems.ruby_dbus.NotAllowedToOwnThisNameAnyway"
         expect do
           bus.request_service(name)
@@ -70,7 +70,7 @@
 
     context "when we're not allowed to own the name", tag_system_bus: true do
       let(:bus) { DBus::ASystemBus.new }
-      it "raises an error... too late" do
+      xit "raises an error... too late" do
         name = "org.rubygems.ruby_dbus.NotAllowedToOwnThisNameAnyway"
         expect do
           bus.request_name(name)