[2205] logged really unexpected exception in manager's dtor.

src/bin/auth/auth_messages.mes

@@ -301,3 +301,11 @@ AUTH_DATASRC_CLIENTS_BUILDER_FAILED or
 AUTH_DATASRC_CLIENTS_BUILDER_FAILED_UNEXPECTED error messages in past
 logs.  If this message appears, the maintenance of the data source
 clients hasn't been working properly for some time.
+
+% AUTH_DATASRC_CLIENTS_SHUTDOWN_UNEXPECTED_ERROR Unexpected error on waiting for data source builder thread
+Some exception happens while waiting for the termination of the
+separate thread for maintaining data source clients.  This shouldn't
+happen in normal conditions; it should be either fatal system level
+errors such as severe memory shortage or some internal bug.  If that
+happens, and if it's not in the middle of terminating b10-auth, it's
+probably better to stop and restart it.

src/bin/auth/datasrc_clients_mgr.h

@@ -128,7 +128,10 @@ public:
             // simply let it go through.
             LOG_ERROR(auth_logger, AUTH_DATASRC_CLIENTS_SHUTDOWN_ERROR).
                 arg(ex.what());
-        } catch (...) {}
+        } catch (...) {
+            LOG_ERROR(auth_logger,
+                      AUTH_DATASRC_CLIENTS_SHUTDOWN_UNEXPECTED_ERROR);
+        }
 
         cleanup();              // see below
     }