uwsgi: Stop using -d option
err.txt in Round10 preview2 was broken.
https://github.com/TechEmpower/TFB-Round-10/blob/master/peak/linux/results-2015-02-26-peak-preview2/latest/logs/bottle-nginx-uwsgi/err.txt
While uwsgi is safe to write errorlog concurrently, other tool may
conflict somewhat.
This commit makes uwsgi writes errorlog to stderr.
It may (and may not) fix the errorlog.