JENKINS-22999 - Git Polling and Git Configuration check fail

When there is a proxy server between Jenkins and the GIT Repository the GIT Polling and GIT Configuration check fail with unable to resolve host error. This is due to the proxy not being set.

This patch set the http_proxy and https_proxy when the repo is http/https, the proxy configuration is set, and there is no NoProxy match.

It does not address proxies that are secured by id/password.