(maint) fix logic for choosing rspec version
(maint) fix logic for choosing rspec version

Depending on the ruby version, we either need 3.1.7 to support ruby 1.8,
but since (at least) ruby 2.2 a newer version of rspec is required.

ndelic0/puppetlabs-mysql,squarit/puppetlabs-mysql,markasammut/puppetlabs-mysql,skyscrapers/puppetlabs-mysql,Adaptavist/puppet-mysql,edestecd/puppetlabs-mysql,simp/puppetlabs-mysql,apa-it/puppetlabs-mysql,apa-it/puppetlabs-mysql,squarit/puppetlabs-mysql,igalic/puppetlabs-mysql,ndelic0/puppetlabs-mysql,breuninger-ecom/puppetlabs-mysql,hundredacres/puppetlabs-mysql,fuel-infra/puppetlabs-mysql,breuninger-ecom/puppetlabs-mysql,DavidS/puppetlabs-mysql,rdo-puppet-modules/puppetlabs-mysql,edestecd/puppetlabs-mysql,rdo-puppet-modules/puppetlabs-mysql,puppetlabs/puppetlabs-mysql,breuninger-ecom/puppetlabs-mysql,jbondpdx/puppetlabs-mysql,fuel-infra/puppetlabs-mysql,hundredacres/puppetlabs-mysql,markasammut/puppetlabs-mysql,Adaptavist/puppet-mysql,simp/puppetlabs-mysql,skyscrapers/puppetlabs-mysql,jbondpdx/puppetlabs-mysql,puppetlabs/puppetlabs-mysql,DavidS/puppetlabs-mysql,igalic/puppetlabs-mysql