Remove unnecessary set driver and instance log level calls

[amogh09]

Summary

If Agent is not started with a logLevel command-line argument then it attempts to set driver and instance log level of the logger using loglevel-driver and loglevel-on-instance command-line arguments regardless of whether they were passed or not. This causes the following misleading error logs to be printed.

{"level":"error","time":"2024-10-01T06:24:05Z","msg":"Driver log level mapping not found","module":"log.go"}
{"level":"error","time":"2024-10-01T06:24:05Z","msg":"Instance log level mapping not found","module":"log.go"}

This PR fixes this issue by making Agent skip setting driver and instance log levels if the corresponding command-line arguments are not passed.

Fixes #4375.

Testing

Ran Agent and verified that the misleading error logs are no longer printed. Log level settings continue to be set and work as before.

New tests cover the changes: no

Description for the changelog

bugfix - Remove unnecessary set driver and instance log level calls

Additional Information

Does this PR include breaking model changes? If so, Have you added transformation functions?

Does this PR include the addition of new environment variables in the README?

Licensing

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.