Usually kernel install is unnecessary, so don't quit if it fails

util/install.sh

@@ -102,7 +102,10 @@ OF13_SWITCH_REV=${OF13_SWITCH_REV:-""}
 function kernel {
     echo "Install Mininet-compatible kernel if necessary"
     sudo apt-get update
-    $install linux-image-$KERNEL_NAME
+    if ! $install linux-image-$KERNEL_NAME; then
+        echo "Could not install linux-image-$KERNEL_NAME"
+        echo "Skipping - assuming installed kernel is OK."
+    fi
 }
 
 function kernel_clean {