[3823] Addressed review comments.

Do not remove duplicates if other MessageInitializers held them.
Also, do not remove message from the dictionary if removing the
duplicate.

src/lib/log/message_initializer.cc

@@ -1,3 +1,4 @@
+
 // Copyright (C) 2011,2015  Internet Systems Consortium, Inc. ("ISC")
 //
 // Permission to use, copy, modify, and/or distribute this software for any
@@ -77,8 +78,18 @@ MessageInitializer::~MessageInitializer() {
         // the dictionary and/or duplicates.
         int i = 0;
         while (values_[i]) {
-            global_logger_duplicates_->remove(values_[i]);
-            global_dictionary_->erase(values_[i], values_[i + 1]);
+            // Check if the unloaded message is registered as duplicate. If it is,
+            // remove it from the duplicates list.
+            LoggerDuplicatesList::const_iterator dup =
+                std::find(global_logger_duplicates_->begin(),
+                          global_logger_duplicates_->end(),
+                          values_[i]);
+            if (dup != global_logger_duplicates_->end()) {
+                global_logger_duplicates_->erase(dup);
+
+            } else {
+                global_dictionary_->erase(values_[i], values_[i + 1]);
+            }
             i += 2;
         }
     }

src/lib/log/tests/message_initializer_1_unittest.cc

@@ -45,7 +45,7 @@ const char* values3[] = {
 };
 
 const char* values4[] = {
-    "GLOBAL8", "global message eight bis",
+    "GLOBAL8", "global message eight",
     "GLOBAL9", "global message nine",
     NULL
 };
@@ -119,11 +119,12 @@ TEST(MessageInitializerTest1, dynamicLoadUnload) {
     EXPECT_EQ("global message eight", global->getText("GLOBAL8"));
     EXPECT_EQ("global message nine", global->getText("GLOBAL9"));
 
-    // Destroy the first initializer. The first two messages should
-    // be unregistered.
+    // Destroy the first initializer. The first message should be removed.
+    // The second message should not be removed because it is also held
+    // by another object.
     init1.reset();
     EXPECT_TRUE(global->getText("GLOBAL7").empty());
-    EXPECT_TRUE(global->getText("GLOBAL8").empty());
+    EXPECT_EQ("global message eight", global->getText("GLOBAL8"));
     EXPECT_EQ("global message nine", global->getText("GLOBAL9"));
 
     // Destroy the second initializer. Now, all messages should be