(FACT-1134) Fix Facter operatingsystem resolution

[MikaelSmith]

Facter 3's operatingsystem fact resolution rearranged the order release
files were searched for so that some RedHat distributions would resolve
to RedHat instead of more specific names, for example OracleLinux.

Restore original ordering with respect to searching specific
distributions before RedHat and SUSE.

[MikaelSmith]

Original search order https://github.com/puppetlabs/facter/blob/2.x/lib/facter/operatingsystem/linux.rb#L241-L286

[peterhuene]

Early return?

[MikaelSmith]

[root@x5nhcn0p0c027pk ~]# cat /etc/oracle-release
Oracle Linux Server release 7.0
[root@x5nhcn0p0c027pk ~]# /opt/puppetlabs/bin/facter os
{
  architecture => "x86_64",
  family => "RedHat",
  hardware => "x86_64",
  name => "OracleLinux",
  release => {
    full => "7.0",
    major => "7",
    minor => "0"
  },
  selinux => {
    config_mode => "enforcing",
    current_mode => "enforcing",
    enabled => true,
    enforced => true,
    policy_version => "28"
  }
}

[MikaelSmith]

Compared to Facter 2.4.4 on the same machine
{"name"=>"OracleLinux", "family"=>"RedHat", "release"=>{"major"=>"7", "minor"=>"0", "full"=>"7.0"}}

[puppetcla]

CLA signed by all contributors.