(FACT-2724) Confine blocks behave differently with Facter 4, causing spec tests to suddenly fail

[BogdanIrimie]

problem

virtual fact was returning nil on physical macOS hosts. The test mocked virtual fact by using

allow(Facter.fact(:virtual)).to receive(:value).and_return('physical')

and because Facter.fact(:virtual) returned nil on physical macOS hosts, the mock was basically

allow(nil).to receive(:value).and_return('physical')

fix

on macOS physiscal host, facter will return virtual => physical

[puppetcla]

CLA signed by all contributors.