Improve log and fix readme doc mismatch issues

[moarychan]

Purpose

Source code does not match the readme doc; improve the log context.

Does this introduce a breaking change?

[ ] Yes
[x] No

Pull Request Type

What kind of change does this Pull Request introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Documentation content changes
[ ] Other... Please describe:

How to Test

Run sample eventhubs/spring-cloud-azure-starter-eventhubs/eventhubs-client.

git clone [repo-address]
cd [repo-name]
git checkout [branch-name]
npm install

• Test the code

What to Check

N/A

Other Information

[rujche]

LGTM.

[rujche]

LGTM.