Remove etc entry from runonce.install

- We have no files for etc, so pbuilder fails on this entry.

Change-Id: Ib869dcfff16ef0163d861160a5b01fb00a119bf3
diff --git a/debian/runonce.install b/debian/runonce.install
index 4e66675..3c29d34 100644
--- a/debian/runonce.install
+++ b/debian/runonce.install
@@ -1,2 +1 @@
 usr /
-etc /