Fix facter mysql version unit test

Author: Daniel Carabas

spec/unit/facter/mysql_version_spec.rb

@@ -8,6 +8,7 @@
   describe 'mysql_version' do
     context 'with value' do
       before :each do
+        Facter::Core::Execution.stubs(:which).returns('fake_mysql_path')
         Facter::Util::Resolution.stubs(:exec).with('mysql --version').returns('mysql  Ver 14.12 Distrib 5.0.95, for redhat-linux-gnu (x86_64) using readline 5.1')
       end
       it {