Ensure that ip_forwarding is always enabled for compute and network

Libvirt gets this in most cases, but it can be disabled.  This is
belts + suspenders + super glue...

Fixes bug 885274

Change-Id: Ifb8d627689800b23cce02a623caa525cd17e507d
diff --git a/stack.sh b/stack.sh
index eead8a1..b67bf16 100755
--- a/stack.sh
+++ b/stack.sh
@@ -886,6 +886,9 @@
     # ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     apt_get install libvirt-bin
 
+    # Force IP forwarding on, just on case
+    sudo sysctl -w net.ipv4.ip_forward=1
+
     # attempt to load modules: network block device - used to manage qcow images
     sudo modprobe nbd || true
 
@@ -967,6 +970,9 @@
     clean_iptables
     rm -rf $NOVA_DIR/networks
     mkdir -p $NOVA_DIR/networks
+
+    # Force IP forwarding on, just on case
+    sudo sysctl -w net.ipv4.ip_forward=1
 fi
 
 # Storage Service