(maint) Exclude specs on 1.8 without activerecord

Nested RSpec example groups using :if filters can override each other.
In 0804eafef7d5dae2010b6fdaa0a86dee3b41f5e9 A new example group was
added with an :if filter that was clobbering the parent :if filter. The
current Gemfile installs activerecord when the :test or :development
groups are used so this was masked in most runs of the spec tests. This
was only unmasked when the specs were run with no features available.

This commit resolves the broken filtering behavior by propagating the
parent example group filter down to the ruby 1.8 child example group.