ChefでUbuntuの multiverse リポジトリを有効にするために以下のレシピを書きました。これで無効状態から有効に変えることはできたのですが、二度目以降がエラーになってしまいます。

execute "enable multiverse" do
    command %Q{ grep -q '^# deb.*multiverse' /etc/apt/sources.list && sed -i '/^# deb.*multiverse/ s/^# //' /etc/apt/sources.list && apt-get update }
    ignore_failure true
end

以下が該当部分のエラーメッセージです。

Recipe: base::default
  * execute[enable multiverse] action run[2015-01-19T16:53:39+00:00] ERROR: execute[enable multiverse] (base::default line 10) had an error: Expected process to exit with [0], but received '1'
---- Begin output of  grep -q '^# deb.*multiverse' /etc/apt/sources.list && sed -i '/^# deb.*multiverse/ s/^# //' /etc/apt/sources.list && apt-get update  ----
STDOUT:
STDERR:
---- End output of  grep -q '^# deb.*multiverse' /etc/apt/sources.list && sed -i '/^# deb.*multiverse/ s/^# //' /etc/apt/sources.list && apt-get update  ----
Ran  grep -q '^# deb.*multiverse' /etc/apt/sources.list && sed -i '/^# deb.*multiverse/ s/^# //' /etc/apt/sources.list && apt-get update  returned 1; ignore_failure is set, continuing

================================================================================
Error executing action `run` on resource 'execute[enable multiverse]'
================================================================================


Mixlib::ShellOut::ShellCommandFailed
------------------------------------
Expected process to exit with [0], but received '1'
---- Begin output of  grep -q '^# deb.*multiverse' /etc/apt/sources.list && sed -i '/^# deb.*multiverse/ s/^# //' /etc/apt/sources.list && apt-get update  ----
STDOUT:
STDERR:
---- End output of  grep -q '^# deb.*multiverse' /etc/apt/sources.list && sed -i '/^# deb.*multiverse/ s/^# //' /etc/apt/sources.list && apt-get update  ----
Ran  grep -q '^# deb.*multiverse' /etc/apt/sources.list && sed -i '/^# deb.*multiverse/ s/^# //' /etc/apt/sources.list && apt-get update  returned 1


Resource Declaration:
---------------------
# In /home/vagrant/chef-solo/cookbooks-2/base/recipes/default.rb

 10: execute "enable multiverse" do
 11:     command %Q{ grep -q '^# deb.*multiverse' /etc/apt/sources.list && sed -i '/^# deb.*multiverse/ s/^# //' /etc/apt/sources.list && apt-get update }
 12:     ignore_failure true
 13: end
 14:



Compiled Resource:
------------------
# Declared in /home/vagrant/chef-solo/cookbooks-2/base/recipes/default.rb:10:in `from_file'

execute("enable multiverse") do
  action "run"
  ignore_failure true
  retries 0
  retry_delay 2
  command " grep -q '^# deb.*multiverse' /etc/apt/sources.list && sed -i '/^# deb.*multiverse/ s/^# //' /etc/apt/sources.list && apt-get update "
  backup 5
  returns 0
  cookbook_name :base
  recipe_name "default"
end

ignore_failure trueを設定してるのでgrepが失敗を返してもレシピ自体は正常終了すると思ったのですが、そうではないのでしょうか？