Update spec/beaker/host/unix/exec_spec.rb

Co-authored-by: Ewoud Kohl van Wijngaarden <ewoud@kohlvanwijngaarden.nl>

spec/beaker/host/unix/exec_spec.rb

@@ -143,7 +143,7 @@ def to_s
 
     describe '#prepend_commands' do
       it 'returns the pc parameter unchanged for all platforms' do
-        allow(instance).to receive(:[]).with(:platform).and_return('notcisco')
+        allow(instance).to receive(:[]).with(:platform).and_return('unix')
         answer_prepend_commands = 'pc_param_unchanged_13579'
         answer_test = instance.prepend_commands('fake_cmd', answer_prepend_commands)
         expect(answer_test).to be === answer_prepend_commands