Fix distcheck after commit 29386d3e

Missing backslash.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Iustin Pop <iustin@google.com>

Makefile.am

@@ -160,7 +160,7 @@ CLEANFILES = \
 	$(man_MANS) \
 	$(manhtml) \
 	tools/kvm-ifup \
-	tools/vcluster-setup
+	tools/vcluster-setup \
 	stamp-directories \
 	stamp-srclinks \
 	$(nodist_pkgpython_PYTHON) \