* grep returns a non-zero exit code if no line matches, causing the

swap task to fail.  So ignore that.

svn path=/nixos/trunk/; revision=19660

modules/tasks/swap.nix

@@ -94,7 +94,7 @@ in
               device=$(readlink -f "$device")
               # Add new swap devices.
               if echo $unused | grep -q "^$device\$"; then
-                unused="$(echo $unused | grep -v "^$device\$")"
+                unused="$(echo $unused | grep -v "^$device\$" || true)"
               else
                 ${utillinux}/sbin/swapon "$device" || true
               fi