[2211] test duplicate mgr holder acquisition instead using auth locker

the latter will soon be deprecated.

src/bin/auth/tests/auth_srv_unittest.cc

@@ -1787,17 +1787,4 @@ TEST_F(AuthSrvTest, DDNSForwardCreateDestroy) {
                 Opcode::UPDATE().getCode(), QR_FLAG, 0, 0, 0, 0);
 }
 
-// We just test the mutex can be locked (exactly once).
-TEST_F(AuthSrvTest, mutex) {
-    isc::util::thread::Mutex::Locker l1(server.getDataSrcClientListMutex());
-    // TODO: Once we have non-debug build, this one will not work, since
-    // we currently use the fact that we can't lock twice from the same
-    // thread. In the non-debug mode, this would deadlock.
-    // Skip then.
-    EXPECT_THROW({
-        isc::util::thread::Mutex::Locker l2(
-            server.getDataSrcClientListMutex());
-    }, isc::InvalidOperation);
-}
-
 }

src/bin/auth/tests/datasrc_clients_mgr_unittest.cc

@@ -189,8 +189,12 @@ TEST(DataSrcClientsMgrTest, holder) {
         EXPECT_TRUE(holder.findClientList(RRClass::IN()));
         EXPECT_FALSE(holder.findClientList(RRClass::CH()));
     }
-}
 
+    // Duplicate lock acquisition is prohibited (only test mgr can detect
+    // this reliably, so this test may not be that useful)
+    TestDataSrcClientsMgr::Holder holder1(mgr);
+    EXPECT_THROW(TestDataSrcClientsMgr::Holder holder2(mgr), isc::Unexpected);
+}
 
 TEST(DataSrcClientsMgrTest, realThread) {
     // Using the non-test definition with a real thread.  Just checking

src/bin/auth/tests/test_datasrc_clients_mgr.h

@@ -51,6 +51,11 @@ public:
     class Locker {
     public:
         Locker(TestMutex& mutex) : mutex_(mutex) {
+            if (mutex.lock_count != mutex.unlock_count) {
+                isc_throw(Unexpected,
+                          "attempt of duplicate lock acquisition");
+            }
+
             ++mutex.lock_count;
             if (mutex.lock_count > 100) { // 100 is an arbitrary choice
                 isc_throw(Unexpected,