[Ubuntu] Configure permissions to vmlinuz image

To be able to use customize-image tool in Tobiko, libguestfs needs
to have access to the vmlinuz image file.
This, at least on Ubuntu based system isn't conigured as it should be
(at least it wasn't in my case).
So this patch adds small function which will ensure vmlinuz permissions
are set correctly and customize-image tool can be used later during the
Tobiko runs.

Change-Id: I65f9f2017f27de7e9f2e1ed4129282cc090484f7

devstack/plugin.sh

@@ -10,6 +10,14 @@ function install_tobiko_deps {
 }
 
 
+function configure_libguestfs_tools {
+    if is_ubuntu; then
+        sudo dpkg-statoverride --update --add root root 0644 \
+            /boot/vmlinuz-`uname -r`
+    fi
+}
+
+
 function configure_tobiko {
     # Ensure any user can write to log file
     local log_dir
@@ -243,6 +251,7 @@ if [[ "$1" == "stack" ]]; then
         install)
             echo_summary "Installing Tobiko dependencies"
             install_tobiko_deps
+            configure_libguestfs_tools
             ;;
         test-config)
             echo_summary "Configuring Tobiko test cases"