Add support for NODEPOOL_RUGYGEMS_PROXY
Add support for NODEPOOL_RUGYGEMS_PROXY

Now that we have a working reverse proxy cache for api.rubygems.org,
add the .gemrc file and start using it.

Change-Id: I6d8cd1d1353fc28469aceb16d487cd9b39eda73b
Signed-off-by: Paul Belanger <e7139c8e6c4ea75cc1c287ce081b2dc0f3ab39ec@redhat.com>

openstack-infra/project-config,openstack-infra/project-config