auto-generated jenkins keys should be added to the jenkins credential list

[ryanj]

I know we need to wrap ssh in order to bypass some issue with known_hosts, but our ssh hacks don't mix well with plugins that allow for ssh credential substitution.

It would be nice to include the auto-generated jenkins system keys in the global credentials list, and then select them from that list when needed.

This could help improve compatibility between OpenShift's Jenkins config and various 3rd party plugins that rely on credentialed access to ssh.