[MODULES-690] - Fix server_package_name been ignored.

* Fix server_package_name been ignored and changed the default
installation to install the mongodb-org version when
manage_package_repo => true .
* Add spec to test the installation using mongodb-org and
mongo-10gen-server.

Exemples:

This code will install mongodb-org (Tested on Red Hat , Debian and Ubuntu )

class {'::mongodb::globals':
  manage_package_repo => true,
}->
class {'::mongodb::server': }->
class {'::mongodb::client': }

This code will install mongodb-10gen (Tested on Debian and Ubuntu)(Tested on Red Hat install mongodb-org because 10gen is obsolete(It's just Red Hat reaction the same is with today's code)

class {'::mongodb::globals':
  server_package_name = 'mongodb-10gen',
  manage_package_repo => true,
}->
class {'::mongodb::server': }->
class {'::mongodb::client': }