Cannot find a resource for preferred_state

This fixes an issue when installing `pear` of `pecl` packages i.e. 

```
php_pear 'mongo'
```

output:

```
...
================================================================================
Error executing action `install` on resource 'php_pear[mongo]'
================================================================================


NameError
---------
Cannot find a resource for preferred_state on ubuntu version 12.04


Cookbook Trace:
---------------
/tmp/vagrant-chef-1/chef-solo-1/cookbooks/php/providers/pear.rb:261:in `pecl?'
/tmp/vagrant-chef-1/chef-solo-1/cookbooks/php/providers/pear.rb:105:in `load_current_resource'


Resource Declaration:
---------------------
# In /tmp/vagrant-chef-1/chef-solo-1/cookbooks/sample/recipes/sample.rb

 33:   php_pear pkg
 34: end



Compiled Resource:
------------------
# Declared in /tmp/vagrant-chef-1/chef-solo-1/cookbooks/sample/recipes/sample.rb:33:in `block in from_file'

php_pear("mongo") do
  action :install
  retries 0
  retry_delay 2
  cookbook_name :sample
  recipe_name "sample"
  package_name "mongo"
end
...
```