🐛 Bug description

LR finder catch errors from Visdom server and thus fails.

tests/ignite/contrib/handlers/test_lr_finder.py:202: AssertionError

------------------------------ Captured log call -------------------------------

ERROR    visdom:__init__.py:619 [Errno 111] Connection refused
ERROR    visdom:__init__.py:619 [Errno 111] Connection refused

https://travis-ci.org/github/pytorch/ignite/jobs/698932904#L3758

Need to inspect and fix that.

Environment

• PyTorch Version (e.g., 1.4):
• Ignite Version (e.g., 0.3.0):
• OS (e.g., Linux):
• How you installed Ignite (conda, pip, source):
• Python version:
• Any other relevant information: