always del Model even in error (#1562)
Summary:
Sometimes there are uncaught errors, so we don't make it to this line that is essential for saving memory.
Pull Request resolved: https://github.com/pytorch/benchmark/pull/1562
Reviewed By: xuzhao9
Differential Revision: D45188052
Pulled By: janeyx99
fbshipit-source-id: 885c4ac575e7382335cb5283c5730ff64676ddd6
