Add support for using the same source for different sensu handlers

[salimane]

Currently it's impossible to use the same source for different handlers. a duplicate file definition exception is thrown. This PR fixes that. With this PR, you can now do:

---
sensu::handlers:
  'hipchat_main_room':
    type: pipe
    source: "puppet:///modules/sensu_module/community-plugins/handlers/notification/hipchat.rb"
    config:
      apikey: my_long_key
      room: Big Alerts
  'hipchat_other_room':
    type: pipe
    source: "puppet:///modules/sensu_module/community-plugins/handlers/notification/hipchat.rb"
    config:
      apikey: my_other_long_key
      room: 'Small Alerts'

cc @jlambert121
Thanks

[jlambert121]

I see the issue, but I'm struggling on putting each handler into its own directory for this somewhat edge case (I say edge because I haven't seen anything about hitting this issue before). What about just wrapping the file resource in handler.pp with an ensure_resource instead? I don't normally like using that because I don't think the code is as explicit, but this seems like it could be a prime use case.

[salimane]

@jlambert121 , I've updated the changes and use ensure_resource instead.
Thanks

[jlambert121]

Thanks!