Avoid trivial memory leak in unit test driver

If we add only a subset of tests to the runner (via --re or --deny_re
options), we're careful to move the other tests to a "rejects" suite so
they'll get deleted there, but the "supertest", the suite holding all
the other tests, wasn't getting deleted in those cases.

This (on top of my earlier fixes, and using the MOOSE suppressions file
for third-party library issues) gets selective valgrind runs of our unit
tests clean for me.

Author: roystgnr

tests/driver.C

@@ -116,11 +116,17 @@ int main(int argc, char ** argv)
   std::string deny_regex_string = "^$";
   deny_regex_string = libMesh::command_line_next("--deny_re", deny_regex_string);
 
+  // We might have to delete the test suite ourselves, after the
+  // runner has deleted whatever subtests it has.
+  std::unique_ptr<CppUnit::Test> owned_suite;
+
   // Recursively add tests matching the regex to the runner object.
   CppUnit::TextUi::TestRunner runner;
 
-  // The Cppunit registry object that knows about all the tests.
+  // The Cppunit registry object that knows about all the tests, and
+  // the test suite it creates.
   CppUnit::TestFactoryRegistry & registry = CppUnit::TestFactoryRegistry::getRegistry();
+  CppUnit::Test * suite = registry.makeTest();
 
   // A test suite container for holding tests not matching the regex. When main's
   // scope ends, this class's destructor will delete the rejected tests
@@ -134,15 +140,17 @@ int main(int argc, char ** argv)
   // Add all tests which match the re to the runner object.
   libMesh::out << "Will run the following tests:" << std::endl;
   const int n_tests_added =
-    add_matching_tests_to_runner(registry.makeTest(),
+    add_matching_tests_to_runner(suite,
                                  allow_regex_string, allow_regex,
                                  deny_regex_string, deny_regex,
                                  runner, rejects);
   if (n_tests_added >= 0)
     libMesh::out << "--- Running " << n_tests_added << " tests in total." << std::endl;
+  if (n_tests_added != -12345)
+    owned_suite.reset(suite);
 #else
   // If no C++11 <regex> just run all the tests.
-  runner.addTest(registry.makeTest());
+  runner.addTest(suite);
 #endif
 
   std::unique_ptr<CppUnit::TestResult> controller;