MXS-2005: Use log manager only after initialization

The log manager functions must not be used before it is initialized.

server/modules/filter/dbfwfilter/test/test_dbfwfilter.cc

@@ -1014,6 +1014,8 @@ int main(int argc, char* argv[])
             {
                 cerr << "error: Could not setup query classifier." << endl;
             }
+
+            mxs_log_finish();
         }
     }
     else

server/modules/filter/masking/test/testrules.cc

@@ -305,6 +305,7 @@ int main()
         {
             rc = (MaskingRulesTester::test_account_handling() == EXIT_FAILURE) ? EXIT_FAILURE : EXIT_SUCCESS;
         }
+        mxs_log_finish();
     }
 
     return rc;