Swap out git08 to new centos7 node

We will put one centos7 git backend into the rotation and see how it
does before switching all backends over to centos7. This gives us newer
git which appears to be much better at managing its memory use when
serving data.

Change-Id: I69c8328a20b28fd85869964972bae2dfb89566bf

manifests/site.pp

@@ -461,7 +461,7 @@ node /^git(-fe\d+)?\.openstack\.org$/ {
       '166.78.46.121',
       '104.239.139.203',
       '104.239.141.178',
-      '104.239.141.187',
+      '104.239.146.131',
     ],
   }
 }