[inputs.tail] Add flag to ignore files if not found and not give error

[deepaksood619]

Feature Request

a flag to ignore if file not present, and not throw error in telegraf logs

Proposal:

Current behavior:

Throws error for file not present

Desired behavior:

Does not throw error and fail silently

Use case:

I don't want to create different configuration for each server because we are using ansible to deploy everything to servers
And I don't want to clutter Elasticsearch with error logs that are not needed

[danielnelson]

Closed by #6540