Bug fix for VPP-104 about not being able to down a sub-if if the super-if is up

Change-Id: I913c9807519aa10e515d12fcfbcbfc22b58f5839
Signed-off-by: Calvin <calvin.ference@gmail.com>
diff --git a/vnet/vnet/interface.c b/vnet/vnet/interface.c
index d84c8b0..24f9cbc 100644
--- a/vnet/vnet/interface.c
+++ b/vnet/vnet/interface.c
@@ -354,7 +354,9 @@
 	{
 	  si_sup = vnet_get_sw_interface (vnm, si->sup_sw_if_index);
 
-	  if (flags != (si_sup->flags & mask))
+	  /* Check to see if we're bringing down the soft interface and if it's parent is up */
+	  if ((flags != (si_sup->flags & mask)) && 
+		  (!((flags == 0) && ((si_sup->flags & mask) == VNET_SW_INTERFACE_FLAG_ADMIN_UP))))
 	    {
 	      error = clib_error_return (0, "super-interface %U must be %U",
 					 format_vnet_sw_interface_name, vnm, si_sup,