Add security context in TestLdapSyncMassive

This should resolve "No authorization" exceptions that occur
in some environments.

(cherry picked from commit 97b8a2b)

testing/story/src/test/java/com/evolveum/midpoint/testing/story/ldap/TestLdapSyncMassive.java

@@ -352,6 +352,7 @@ public void test232UserRecomputeParallel() throws Exception {
         int segmentSize = users.size() / NUMBER_OF_TEST_THREADS;
         ParallelTestThread[] threads = multithread(
                 (threadIndex) -> {
+                    login(userAdministrator.clone());
                     for (int i = segmentSize * threadIndex; i < segmentSize * threadIndex + segmentSize; i++) {
                         PrismObject<UserType> user = users.get(i);
                         reconcile(user);