place default case last in selectors

According to the selector documentation (https://docs.puppetlabs.com/puppet/latest/reference/lang_conditional.html#selectors), the default case should be last:

"Cases are compared in the order that they are written in the manifest; thus, the default case (if any) must be at the end of the list."

This is fixed in 3.7+ but would be nice to fix in this module for people using < 3.7

See also https://tickets.puppetlabs.com/browse/PUP-2642