[1207] use test_db in setup for command loadzone test

It isn't actually used by the test, but by not setting any db, the default db would've been created (and not cleaned up, making distcheck fail for leaving files around)

src/bin/auth/tests/command_unittest.cc

@@ -297,7 +297,9 @@ TEST_F(AuthCommandTest,
                               "      }"
                               "    ]"
                               "  }"
-                              "]}"));
+                              "],"
+                              " \"database_file\": \"" + test_db + "\""
+                              "}"));
     module_session.setLocalConfig(map);
     server_.setConfigSession(&module_session);