Fix dump authentication test

js/server/modules/@arangodb/users.js

@@ -307,6 +307,18 @@ exports.document = function(username) {
   return convertToLegacyFormat(user);
 };
 
+exports.exists = function(username) {
+  try {
+    exports.document(username);
+    return true;
+  } catch (e) {
+    if (e.errNum == arangodb.errors.ERROR_USER_NOT_FOUND.code) {
+      return false;
+    }
+    throw e;
+  }
+}
+
 // checks whether a combination of username / password is valid.
 exports.isValid = function(username, password) {
   const users = getStorage();

js/server/tests/dump/dump-authentication-setup.js

@@ -42,11 +42,10 @@
 
   // create user in _system database
   require("@arangodb/users").save("foobaruser", "foobarpasswd", true);
+  require("@arangodb/users").grantDatabase("foobaruser", "_system");
+  require("@arangodb/users").grantDatabase("foobaruser", "UnitTestsDumpSrc");
   db._useDatabase("UnitTestsDumpSrc");
 
-  // create user in target database
-  require("@arangodb/users").save("foobaruser", "foobarpasswd", true);
-
   var endpoint = arango.getEndpoint();
 
   arango.reconnect(endpoint, "UnitTestsDumpSrc", "foobaruser", "foobarpasswd");

js/server/upgrade-database.js

@@ -530,7 +530,9 @@
 	  if (args && args.users) {
 	    args.users.forEach(function(user) {
 	      try {
+                if (!userManager.exists(user.username)) {
                   userManager.save(user.username, user.passwd, user.active, user.extra || {});
+                }
 	      } catch (err) {
 		logger.warn("could not add database user '" + user.username + "': " +
 		  String(err) + " " +