Fix log output of `SmtpResponseParser`

[cketti]

Checklist

• [X] I have used the search function to see if someone else has already submitted the same bug report.
• [X] I will describe the problem with as much detail as possible.

App version

2205202769770bc37feb98414bb8a1ae084b9c98

Where did you get the app from?

No response

Android version

all

Device model

No response

Steps to reproduce

See log attached to #6062

Expected behavior

Have nice log output.

Actual behavior

• The log contains "SMTP response data on parser error" twice. Find out why that is and if it needs to be fixed.
• SmtpResponseParser.readHelloResponse() doesn't clear logBuffer, so the greeting appears under "SMTP response data on parser error" even though it was parsed without error.

When fixing this please add tests to make sure this doesn't happen again.

Logs

No response