Fix apache listen ports attribute

[legal90]

In cookbook apache2 v3.2.0 the attribute was changed and renamed:
node.default['apache']['listen_ports'] -> node.default['apache']['listen']

This change causes the following error with apache2 cookbook 3.2.0 and higher:

         NoMethodError
         -------------
         undefined method `include?' for nil:NilClass

         Cookbook Trace:
         ---------------
           /tmp/kitchen/cache/cookbooks/stash/recipes/apache2.rb:1:in `from_file'
           /tmp/kitchen/cache/cookbooks/stash/recipes/default.rb:16:in `from_file'

         Relevant File Content:
         ----------------------
         /tmp/kitchen/cache/cookbooks/stash/recipes/apache2.rb:

           1>> node.set['apache']['listen_ports'] = node['apache']['listen_ports'] + [node['stash']['apache2']['port']] unless node['apache']['listen_ports'].include?(node['stash']['apache2']['port'])
           2:  node.set['apache']['listen_ports'] = node['apache']['listen_ports'] + [node['stash']['apache2']['ssl']['port']] unless node['apache']['listen_ports'].include?(node['stash']['apache2']['ssl']['port'])

This PR fixes that issue.

[atikhono]

+1

[bflad]

Would a begin...rescue block here allow supporting both and not require the dependency version pinning?