Duplicate default shellout timeout from 10mins to 20mins

10 minutes may not be enough as a default, installing java package takes 15 minutes in a 512K DSL and i get the following error:

```
ERROR: package[openjdk-7-jdk] (java::openjdk line 44) had an error: Mixlib::ShellOut::CommandTimeout

Compiled Resource:
------------------
# Declared in /home/vagrant/chef-solo/cookbooks-2/java/recipes/openjdk.rb:44:in `block in from_file'
package("openjdk-7-jdk") do
  action :install
  retries 0
  retry_delay 2
  package_name "openjdk-7-jdk"
  version "7u25-2.3.10-1ubuntu0.12.04.2"
  cookbook_name :java
  recipe_name "openjdk"
end
```