Allow for configuration of apt/yum repo when installing on linux systems

The update will check the version attribute, if is 13.x.x.x it will use the old repo, otherwise the new one is used.

There is an additional version 13 test with test-kitchen to verify the use of an older repo. The version string is added to the agent defaults file as a comment to be able to easily determine the version of the agent.

Default test has been updated to test for the current default version 14.2.0-377.