Fix for log_dir access in trainer
This pull request **introduces 1 alert** when merging be2e4ab037277ddc4832ac2dc36155fc3ddccc63 into db60a786c71767478a49dfcad772718f9d4878d2 - [view on LGTM.com](https://lgtm.com/projects/g/NVIDIA/NeMo/rev/pr-97c11b343a84e9d6d8a330403161e07698220e3c)

**new alerts:**

* 1 for Except block handles &#39;BaseException&#39;
Signed-off-by: Oleksii Kuchaiev <okuchaiev@nvidia.com>