logging: remove unuseful fsync

[giuseppe]

trafficstars

the file is going to be removed few lines later with rename():

	/* Replace the previous file */
	if (rename(k8s_log_path_tmp, k8s_log_path) < 0) {
		pexit("Failed to rename log file");
	}

so there is no point in the expensive sync call since the file is not supposed to be persisted after a reboot.