Prevent AWS credentials refresh from stopping on exception

[aYukiSekiguchi]

If aws_credentials() fails due to an unstable network or other issues, it throws an exception. This stops timer_execute() from repeating its block, preventing OpenSearchOutput from updating @_aws_credentials. As a result, @_aws_credentials will expire.

This commit catches the exception and prevents it from propagating to timer_execute(), ensuring continuous credential updates.