(maint) set aio_agent_version for consistency

Because `aio_agent_version` fact comes from facterdb
it can have different values for different platforms,
which can cause CI failures.

Author: gimmyxd

spec/classes/puppet_agent_spec.rb

@@ -137,7 +137,7 @@ def global_facts(facts, os)
 
             context 'with mismatching digest algorithms' do
               let(:facts) do
-                global_facts(facts, os).merge(puppet_digest_algorithm: 'md5')
+                global_facts(facts, os).merge(puppet_digest_algorithm: 'md5', aio_agent_version: '6.17.0')
               end
 
               it { is_expected.not_to compile }