Adapt rubygem-mongo to the new name schema

Use the new schema for rubygem in SLE12 and openSUSE 13.2.
platform_family is always suse and platform can be suse (for backward compat, it is sles) and opensuse. That have been added to obai 7, so it is available on chef >= 11 only. On chef <= 10 you've got only platform and platform_version as identifier because platform_fanily is always suse as well.