(PUP-2944) Use osfamily to choose yum as a default

This is a re-submission of PR #1360. Using `operatingsystem` instead of `osfamily` means that some Red Hat derivatives, notable Oracle Linux and Scientific Linux, don't actually receive a default package provider. Yum just happens to win because it is suitable and has a high "specificity" score. However, if some other suitable provider happens to be installed that matches (or exceeds) Yum in specificity, an alphabetical sort will be used as a tie-breaker and Yum will loose.

Chaos ensues.