contint: move apache proxy configuration to module

Continuous integration has two internal webservices (Jenkins and Zuul)
which are exposed publicly via an Apache proxy. This patch moves the
definitions under the contint module and factor out common code in a new
contint::proxy_common class.

The Zuul proxy is included in the role::zuul::* class.
The Jenkins proxy is included from the old misc::contint::test::jenkins
which is roughly the equivalent of a role class.

Change-Id: Ia140f6ed7ab9dc12d41422f109750e4018211516
Merge "contint: move apache proxy configuration to module" into production