Add persistence.xml to the war files (#293)

* Add persistence.xml to the war files
* Always use the DummyJpaTransactionManager

Use the DJTM until we get all of the dependencies set up for all of the
environments.

This shouldn't affect any of the unit tests, these use the
JpaTransactionManagerRule to set up a local database and connection.

This fixes the App Engine build.

appengine_war.gradle

@@ -25,14 +25,19 @@ project.convention.plugins['war'].webAppDirName =
 
 apply plugin: 'com.google.cloud.tools.appengine'
 
+def coreResourcesDir = "${rootDir}/core/build/resources/main"
+
 // Get the web.xml file for the service.
 war {
     webInf {
         from "../../core/src/main/java/google/registry/env/common/${project.name}/WEB-INF"
+
+        from("${coreResourcesDir}/META-INF/persistence.xml") {
+            into "classes/META-INF"
+        }
     }
 }
 
-def coreResourcesDir = "${rootDir}/core/build/resources/main"
 war {
     from("${coreResourcesDir}/google/registry/ui/html") {
         include "*.html"