(#16081) Facter reports bogus arch on AIX

Without this patch applied facter reports the hardware model of the system rather than the processor architecture.

For example,

root@l488pp139_pub[/software/pe-aix/init] > /opt/puppet/bin/facter
architecture => IBM,9179-MHB

With the patch, the architecture for this system is:

l488pp056_pub > facter architecture
PowerPC_POWER7

while the hardwaremodel remains:

l488pp056_pub > facter hardwaremodel
IBM,9179-MHB
Merge branch 'pull-532' into stable

This closes GH-532.