Add rubygems dependency for puppet-lint

Since we are using the 'gem' provider from puppet, we need to make sure
rubygems is actually installed.

I've also moved our Rakefile to the top level so our gate-ci-puppet-lint
job is able to execute it.

Change-Id: Id37e6aa3ea1d9191a997e29e9b6ba61f68c8c265
Signed-off-by: Paul Belanger <paul.belanger@polybeacon.com>
Reviewed-on: https://review.openstack.org/13778
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins

modules/jenkins/manifests/slave.pp

@@ -38,6 +38,7 @@ class jenkins::slave($ssh_key, $sudo = false, $bare = false, $user = true) {
                  "python-libvirt",
                  "python-zmq", # zeromq unittests (not pip installable)
                  "python3-all-dev",
+                 "rubygems",
                  "sqlite3",
                  "unzip",
                  "wget",
@@ -72,8 +73,9 @@ class jenkins::slave($ssh_key, $sudo = false, $bare = false, $user = true) {
     ]
 
     package { $gem_packages:
-      ensure => latest,
+      ensure   => latest,
       provider => gem,
+      require  => Package['rubygems'],
     }
 
     package { 'git-review':