CTestTestMemcheck: Tolerate trailing "==..." lines from valgrind

When tests

 CTestTestMemcheckDummyPurify
 CTestTestMemcheckDummyValgrind
 CTestTestMemcheckDummyValgrindPrePost
 CTestTestMemcheckDummyValgrindIgnoreMemcheck

run inside a "ctest -T Memcheck" the parent valgrind may add extra lines
starting with "==" to the end of the output.  Tolerate this without
failing.
CTestTestMemcheck: Tolerate trailing "==..." lines from valgrind

When tests

 CTestTestMemcheckDummyPurify
 CTestTestMemcheckDummyValgrind
 CTestTestMemcheckDummyValgrindPrePost
 CTestTestMemcheckDummyValgrindIgnoreMemcheck

run inside a "ctest -T Memcheck" the parent valgrind may add extra lines
starting with "==" to the end of the output.  Tolerate this without
failing.
Merge topic 'cleanup-CTestTestMemcheck' into next

88ae058 CTestTestMemcheck: Tolerate trailing "==..." lines from valgrind
Merge topic 'cleanup-CTestTestMemcheck' into next

8f0bb35 CTestTestMemcheck: Tolerate trailing "==..." lines from valgrind