Expose jenkins_ssh_public_key parameter in openstack_project::jenkins

The jenkins ssh public key is not parameterized in the class,
it's currently hardcoded and referenced from openstack_project::init.pp.
Adding parameter allows user to use its own jenkins public ssh key.

Change-Id: I20c99ffe7c9d462f91a9d1cc580302e45eaae3ed
Merge "Expose jenkins_ssh_public_key parameter in openstack_project::jenkins"