Rewrite vagrant upgrade test's dependency resolution

This is cleaner and it doesn't fail in Jenkins. I'm not sure
why the old way failed in jenkins but not locally, but computers
are basically magic so I take what I can get. Here is a jenkins
failure:
https://elasticsearch-ci.elastic.co/job/elastic+elasticsearch+master+packaging-tests/238/consoleFull

qa/vagrant/build.gradle

@@ -92,15 +92,11 @@ configurations {
 repositories {
   mavenCentral() // Try maven central first, it'll have releases before 5.0.0
   /* Setup a repository that tries to download from
-    https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-[revision].[ext]
-    which should work for 5.0.0+. This isn't a real ivy repository so we have
-    to fake the ivy.xml file locally but it gets the job done. */
+    https://artifacts.elastic.co/downloads/elasticsearch/[module]-[revision].[ext]
+    which should work for 5.0.0+. This isn't a real ivy repository but gradle
+    is fine with that */
   ivy {
-    url "https://artifacts.elastic.co/downloads/"
-    layout "pattern", {
-      artifact "elasticsearch/elasticsearch-[revision].[ext]"
-      ivy "file:$projectDir/ivy.xml"
-    }
+    artifactPattern "https://artifacts.elastic.co/downloads/elasticsearch/[module]-[revision].[ext]"
   }
 }
 

qa/vagrant/ivy.xml

@@ -1,6 +0,0 @@
-<ivy-module version="2.0">
-  <!-- Cheating ivy repository so we can resolve deb and rpm artifacts from
-    https://artifacts.elastic.co/downloads/  which isn't a maven or ivy
-    repository. -->
-  <info organisation="org.elasticsearch" module="elasticsearch"/>
-</ivy-module>