Re #8362. Add a suppressions file for the DataObjects tests.

Valgrind complains about an OpenMP call within the EventList test.
Suppress this warning as we can't do much about it anyway, even if
it is real.
Re #8362. Fix potential memory leak, shown in test.

The list of objects that were at some point locked was not being
deleted in the destructor.
Re #8362. Fix what looks to be an unconsequential typo.
Merge remote-tracking branch 'origin/bugfix/8362_dataobjects_memory_leaks'