AIX hardwaremodel (os -> hardware) fact is non-standard

Was setting up rspec testing on a module after porting it to AIX and the facts are not being found. Part of the problem is that the default "hardwaremodel" filter is `x86_64`. It does have other OS cases for Solaris (i86pc) and BSD (amd64) for example. While we could add a case for AIX https://github.com/mcanevet/rspec-puppet-facts/issues/69 . The problem is, as I started looking, it looks like the "hardwaremodel" is populated with the actual product name model of the machine (such as "IBM,8284-22A"), while other OS's seem to use something like the processor architecture (x86_64). I think that hardware information belongs in a different fact, like maybe productname (based on what I am seeing on OSX) and the hardwaremodel fact should be "powerpc"