rpm: own /lib/modules only in Fedora >= 19

Previously it was owned by filesystem package.

rpm_spec/core-vm-kernel-placeholder.spec

@@ -29,4 +29,6 @@ Placeholder for kernel package as it is managed by Dom0.
 mkdir -p $RPM_BUILD_ROOT/lib/modules
 
 %files
+%if %{fedora} > 18
 %dir /lib/modules
+%endif