fix: missing logs on pytest failures

[adiholden]

Today we save the instance log path to a file after starting instance
` self.log_files = self.get_logs_from_psutil()

    last_log_file = open("/tmp/last_test_log_files.txt", "a")

    for log in self.log_files:
        last_log_file.write(log + "\n")`

after that we check if test failed and if so copy the log files /tmp/failed
in function copy_failed_logs_and_clean_tmp_folder

The problem:

1. copy_failed_logs_and_clean_tmp_folder runs before we shutdown the server which is why we have some log lines missing if test fails
2. we have log files only if instance started successfuly

We want to fix the logic by:

1. use --log_dir flag for each test this way we will know where we will store the log files and will not need to use get_logs_from_psutil
2. check if the test failed copy the log files only after instance.stop()