Really install xen-scrub-pages dracut module

Fixes 456fe99 "Disable scrubbing memory pages during initial balloon down"
QubesOS/qubes-issues#1963

dracut/Makefile

@@ -2,3 +2,4 @@ install:
 	$(MAKE) -C simple
 	$(MAKE) -C full-dmroot
 	$(MAKE) -C full-modules
+	$(MAKE) -C xen-balloon-scrub-pages

rpm_spec/qubes-kernel-vm-support.spec.in

@@ -52,6 +52,7 @@ make install-fedora-kernel-support DESTDIR=%{buildroot}
 /usr/lib/dracut/modules.d/90qubes-vm
 /usr/lib/dracut/modules.d/90qubes-vm-modules
 /usr/lib/dracut/modules.d/90qubes-vm-simple
+/usr/lib/dracut/modules.d/80xen-scrub-pages
 /usr/src/u2mfn-%{version}/
 /usr/sbin/qubes-prepare-vm-kernel
 %config(noreplace) /etc/default/grub.qubes-kernel-vm-support